This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). Introns are regions often found in eukaryote genes which are removed in the splicing process (after the DNA is transcribed into RNA): only the exons encode the protein. This diagram labels a region of only 40 or so bases as a gene. In reality most genes are hundreds of times larger, and the relationships between Introns and exons can be highly complex.

Genetics glossary A-F Adenine One of the four nucleotide bases in DNA or RNA; pairs with thymine in DNA or uracil in RNA. Gene may refer to: Gene, unit of heredity in living organisms Gene, common first name Gene, the antagonist of Metal Gear Solid: Portable Ops. ... Animation of a section of DNA rotating. ... Description: This image shows the coding region in a segment of eukaryotic DNA. Source: [1] (file) License: All of the illustrations in the Talking Glossary of Genetics are freely available and may be used without special permission. ... Description: This image shows the coding region in a segment of eukaryotic DNA. Source: [1] (file) License: All of the illustrations in the Talking Glossary of Genetics are freely available and may be used without special permission. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Diagram of the location of introns and exons within a gene. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... In genetics, splicing is a modification of genetic information after transcription, in which introns of precursor messenger RNA (pre-mRNA) are removed and exons of it are joined. ... An exon is any region of DNA within a gene, that is transcribed to the final messenger RNA (mRNA) molecule, rather than being spliced out from the transcribed RNA molecule. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... This is a glossary of terms commonly used in the study of genetics and related disciplines in biology. ... For the programming language Adenine, see Adenine (programming language). ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Left: An RNA strand, with its nitrogenous bases. ... For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ... Uracil is a pyrimidine which is common and naturally occurring. ... Allele One of multiple alternative forms of a single gene, each of which is a viable DNA sequence occupying a given position, or locus on a chromosome. For example, in humans, one allele of the eye-color gene produces blue eyes and another allele of the eye-color gene produces brown eyes. For the hard rock band, see Allele (band). ... Base pair A pair of nucleotide bases on complementary DNA or RNA strands organized in a double helix. Base pairs, of a DNA molecule. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Left: An RNA strand, with its nitrogenous bases. ... Chromosome A molecular "package" for carrying DNA in cells, organized as two double-helical DNA molecules that encode many genes. Some simple organisms have only one chromosome made of circular DNA, while most eukaryotes have multiple chromosomes made of linear DNA. Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Cytosine One of the four nucleotide bases in DNA or RNA; pairs with guanine. Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Left: An RNA strand, with its nitrogenous bases. ... Guanine is one of the five main nucleobases found in the nucleic acids DNA and RNA; the others being adenine, cytosine, thymine, and uracil. ... DNA A polymeric molecule made of deoxyribonucleotides, hence then name deoxyribonucleic acid. Most often has the form of a "double helix", which consists of two paired DNA molecules and resembles a ladder that has been twisted. The "rungs" of the ladder are made of base pairs, or nucleotides with complementary hydrogen bonding patterns. The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... A deoxyribonucleotide is the monomer, or single unit, of DNA, or deoxyribonucleic acid. ... The Double-Helix are an alien race in the Wing Commander science fiction series. ... Base pairs, of a DNA molecule. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... In chemistry, a hydrogen bond is a type of attractive intermolecular force that exists between two partial electric charges of opposite polarity. ... G-Z Gene The unit of heredity in living organisms, typically encoded in a sequence of nucleotide monomers that make up a long strand of DNA, or deoxyribonucleic acid. A particular gene can have multiple different forms, or alleles, which are defined by different sequences of DNA. For the hard rock band, see Allele (band). ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Gene expression The process in which the infomation encoded in a gene is converted into a form useful for the cell. The first step is transcription, which produces a messenger RNA molecule complementary to the DNA molecule on which a gene is encoded. For protein-coding genes, the second step is translation, in which the messenger RNA is read by the ribosome to produce a protein. Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... The life cycle of an mRNA in a eukaryotic cell. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Gene pool The sum of all the alleles shared by members of a single population. The gene pool of a species or a population is the complete set of unique alleles that would be found by inspecting the genetic material of every living member of that species or population. ... Genetics The field of biology that studies genes and their inheritance. This article is about the general scientific term. ... Genome The total complement of genetic material contained in an organism or cell. In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Life on Earth redirects here. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Genotype The complement of alleles present in a particular individual's genome that give rise to the individual's phenotype. This article does not cite any references or sources. ... For the hard rock band, see Allele (band). ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... Guanine One of the four nucleotide bases in DNA or RNA; pairs with cytosine. Guanine is one of the five main nucleobases found in the nucleic acids DNA and RNA; the others being adenine, cytosine, thymine, and uracil. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Left: An RNA strand, with its nitrogenous bases. ... Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at... Locus A location on a chromosome where a particular gene resides. The word locus (plural loci) is Latin for place: In biology and evolutionary computation, a locus is the position of a gene (or other significant sequence) on a chromosome. ... Phenotype The observable physical or behavioral traits of an organism, largely determined by the organism's genotype. Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... Life on Earth redirects here. ... This article does not cite any references or sources. ... Protein A linear polymeric molecule made of of amino acids linked by peptide bonds. Proteins carry out the majority of chemical reactions that occur inside the cell. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... This article is about the class of chemicals. ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... For other uses, see Chemical reaction (disambiguation). ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... RNA A polymeric molecule made of ribonucleotides, hence the name ribonucleic acid, similar to but less stable than DNA. One type, messenger RNA, plays an important role in gene expression. Ribosomes are also made largely of RNA. Left: An RNA strand, with its nitrogenous bases. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... A ribonucleotide is a nucleotide in which a purine or pyrimidine base is linked to a ribose molecule. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... The life cycle of an mRNA in a eukaryotic cell. ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... Thymine One of the four nucleotide bases in DNA; pairs with adenine. In RNA, thymine is replaced with uracil. For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... For the programming language Adenine, see Adenine (programming language). ... Left: An RNA strand, with its nitrogenous bases. ... Uracil is a pyrimidine which is common and naturally occurring. ... Transcription The first step in gene expression, in which a messenger RNA molecule complementary to particular gene encoded in DNA is synthesized by enzymes called RNA polymerases. To produce a functional protein, transcription is followed by translation. A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... The life cycle of an mRNA in a eukaryotic cell. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... This article does not cite any references or sources. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... Translation The second step in gene expression, in which a messenger RNA molecule is read by the ribosome to produce a functional protein. Translation is always preceded by transcription. Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... The life cycle of an mRNA in a eukaryotic cell. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Uracil One of the four nucleotide bases in RNA; pairs with adenine. In DNA, uracil is replaced with thymine. Uracil is a pyrimidine which is common and naturally occurring. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... Left: An RNA strand, with its nitrogenous bases. ... For the programming language Adenine, see Adenine (programming language). ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ...

A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions.^[1][2] The physical development and phenotype of organisms can be thought of as a product of genes interacting with each other and with the environment^[3]. A concise definition of gene taking into account complex patterns of regulation and transcription, genic conservation and non-coding RNA genes, has been proposed by Gerstein et al.^[4] "A gene is a union of genomic sequences encoding a coherent set of potentially overlapping functional products". In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... This article or section does not adequately cite its references or sources. ... Views of a Foetus in the Womb, Leonardo da Vinci, ca. ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ...

In cells, genes consist of a long strand of DNA that contains a promoter, which controls the activity of a gene, and a coding sequence, which determines what the gene produces. When a gene is active, the coding sequence is copied in a process called transcription, producing an RNA copy of the gene's information. This RNA can then direct the synthesis of proteins via the genetic code. However, RNAs can also be used directly, for example as part of the ribosome. These molecules resulting from gene expression, whether RNA or protein, are known as gene products. The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A promoter is a regulatory region of DNA located upstream (towards the 5 region) of a gene, providing a control point for regulated gene transcription. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... Left: An RNA strand, with its nitrogenous bases. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A gene product is the biochemical material, either RNA or protein, resulting from expression of a gene. ...

Genes often contain regions that do not encode products, but regulate gene expression. The genes of eukaryotic organisms can contain non-coding regions called introns that are removed from the messenger RNA in a process called splicing. The regions encoding gene products are called exons. In eukaryotes, a single gene can encode multiple proteins, which are produced through the creation of different arrangements of exons through alternative splicing. In prokaryotes (bacteria and archaea), introns are less common and genes often contain a single uninterrupted stretch of DNA, called a cistron, that codes for a product. Prokaryotic genes are often arranged in groups called operons with promoter and operator sequences that regulate transcription of a single long RNA. This RNA contains multiple coding sequences. Each coding sequence is preceded by a Shine-Dalgarno sequence that ribosomes recognize. Gene regulation is the general term for cellular control of protein synthesis at the DNA-RNA transcription step. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Diagram of the location of introns and exons within a gene. ... In genetics, splicing is a modification of genetic information after transcription, in which introns of precursor messenger RNA (pre-mRNA) are removed and exons of it are joined. ... An exon is any region of DNA within a gene, that is transcribed to the final messenger RNA (mRNA) molecule, rather than being spliced out from the transcribed RNA molecule. ... Prokaryotic bacteria cell structure Prokaryotes (IPA: //) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Phyla Crenarchaeota Euryarchaeota Korarchaeota Nanoarchaeota ARMAN The Archaea (), or archaebacteria, are a major group of microorganisms. ... An operon is a group of genes including an operator, a common promoter, and one or more structural genes that are controlled as a unit to produce messenger RNA (mRNA). ... A promoter is a regulatory region of DNA located upstream (towards the 5 region) of a gene, providing a control point for regulated gene transcription. ... In mathematics, an operator is a function that performs some sort of operation on a number, variable, or function. ... Look up Transcription in Wiktionary, the free dictionary. ... Left: An RNA strand, with its nitrogenous bases. ... The Shine-Dalgarno Sequence (AGGAGGU) is the signal for initiation of protein biosynthesis in bacterial mRNA. It is located 5 of the first coding AUG, and consists primarily, but not exclusively, of purines. ...

The total set of genes in an organism is known as its genome. An organism's genome size is generally lower in prokaryotes, both in number of base pairs and number of genes, than even single-celled eukaryotes. However, there is no clear relationship between genome sizes and complexity in eukaryotic organisms. One of the largest known genomes belongs to the single-celled amoeba Amoeba dubia, with over 670 billion base pairs, some 200 times larger than the human genome.^[5] The estimated number of genes in the human genome has been repeatedly revised downward since the completion of the Human Genome Project; current estimates place the human genome at just under 3 billion base pairs and about 20,000–25,000 genes.^[6]. A recent Science article gives a final number of 20,488, with perhaps 100 more yet to be discovered .^[7] The gene density of a genome is a measure of the number of genes per million base pairs (called a megabase, Mb); prokaryotic genomes have much higher gene densities than eukaryotes. The gene density of the human genome is roughly 12–15 genes/Mb.^[8] In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Genome size refers to the total amount of DNA contained within one copy of a genome. ... Prokaryotic bacteria cell structure Prokaryotes (IPA: //) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. ... Base pairs, of a DNA molecule. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... For other uses, see Amoeba (disambiguation). ... A graphical representation of the normal human karyotype. ... The Human Genome Projects (HGP) goal is to understand the genetic make-up of the human species by determining the DNA sequence of the human genome and the genome of a few model organisms. ... Science is the journal of the American Association for the Advancement of Science (AAAS). ...

History

Main article: History of genetics

The existence of genes was first suggested by Gregor Mendel (1822-1884), who, in the 1860s, studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring. He spent over 10 years of his life on one experiment. Although he did not use the term gene, he explained his results in terms of inherited characteristics. Mendel was also the first to hypothesize independent assortment, the distinction between dominant and recessive traits, the distinction between a heterozygote and homozygote, and the difference between what would later be described as genotype and phenotype. Mendel's concept was given a name by Hugo de Vries in 1889, who, at that time probably unaware of Mendel's work, in his book Intracellular Pangenesis coined the term "pangen" for "the smallest particle [representing] one hereditary characteristic"^[9]. Wilhelm Johannsen abbreviated this term to "gene" ("gen" in Danish and German) two decades later. Gregor Mendel, the father of genetics The history of genetics is generally held to have started in 1865 when an Austrian monk, Gregor Mendel published his work on pea plants. ... “Mendel” redirects here. ... // The First Transcontinental Railroad in the USA was built in the six year period between 1863 and 1869. ... Binomial name L. Percentages are relative to US recommendations for adults. ... Look up Hypothesis in Wiktionary, the free dictionary. ... In genetics, Independent assortment is the process of random segregation and assortment of chromosomes during gametogenesis to produce genetically unique gametes. ... In genetics, the term dominant gene refers to the allele that causes a phenotype that is seen in a heterozygous genotype. ... In genetics, the term recessive gene refers to an allele that causes a phenotype (visible or detectable characteristic) that is only seen in a homozygous genotype (an organism that has two copies of the same allele). ... An organism is a heterozygote or heterozygous for a gene or trait if it has different alleles at the genes locus for each homologous chromosome. ... This article or section does not cite its references or sources. ... This article does not cite any references or sources. ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... Hugo Marie de Vries (16th February 1848-21st May 1935), a Dutch biologist, was one of three men - see also Carl Correns and Erich von Tschermak - who in 1900 rediscovered Gregor Mendels work on genetics. ... Wilhelm Ludvig Johannsen (February 3, 1857 - November 11, 1927) was a Danish botanist. ...

In the early 1900s, Mendel's work received renewed attention from scientists. In 1910, Thomas Hunt Morgan showed that genes reside on specific chromosomes. He later showed that genes occupy specific locations on the chromosome. With this knowledge, Morgan and his students began the first chromosomal map of the fruit fly Drosophila. In 1928, Frederick Griffith showed that genes could be transferred. In what is now known as Griffith's experiment, injections into a mouse of a deadly strain of bacteria that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse. Thomas Hunt Morgan (September 25, 1866 – December 4, 1945) was an American geneticist and embryologist. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Binomial name Meigen, 1830[1] Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order of the flies. ... Frederick Griffith (1879 - 1941) was a British medical officer. ... Griffiths experiment was conducted in 1928 by Frederick Griffith which was one of the first experiments suggesting that bacteria are capable of transferring genetic information, otherwise known as the “transforming principle”, which was later discovered to be DNA. Griffith used two strains of Pneumococcus (which infects mice), a S... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ...

In 1941, George Wells Beadle and Edward Lawrie Tatum showed that mutations in genes caused errors in certain steps in metabolic pathways. This showed that specific genes code for specific proteins, leading to the "one gene, one enzyme" hypothesis.^[10] Oswald Avery, Collin Macleod, and Maclyn McCarty showed in 1944 that DNA holds the gene's information. In 1953, James D. Watson and Francis Crick demonstrated the molecular structure of DNA. Together, these discoveries established the central dogma of molecular biology, which states that proteins are translated from RNA which is transcribed from DNA. This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses. Beadle won a Nobel Prize in 1958 George Wells Beadle (October 22, 1903 – June 9, 1989) was an American scientist in the field of genetics. ... Tatum won the Nobel Prize for his work in genetics Edward Lawrie Tatum (December 14, 1909 – November 5, 1975) was an American geneticist. ... In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ... Oswald Theodore Avery (October 21, 1877–1955) was a Canadian-born American physician and medical researcher. ... Collin M. Macleod (1909-1972) was a geneticist. ... Maclyn McCarty (June 9, 1911–January 2, 2005) was an American geneticist. ... James Dewey Watson (born April 6, 1928) is an American molecular biologist, best known as one of the co-discoverers of the structure of DNA. Watson, Francis Crick, and Maurice Wilkins were awarded the 1962 Nobel Prize in Physiology or Medicine for their discoveries concerning the molecular structure of nucleic... Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004) was an English molecular biologist, physicist, and neuroscientist, who is most noted for being one of the co-discoverers of the structure of the DNA molecule in 1953. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Information flow in biological systems The central dogma of molecular biology was first enunciated by Francis Crick in 1958[1] and re-stated in a Nature paper published in 1970:[2] POSTLEWAITE IS A TOOL The central dogma of molecular biology deals with the detailed residue-by-residue transfer of... Left: An RNA strand, with its nitrogenous bases. ... Reverse transcriptase is an enzyme used by all retroviruses and retrotransposons that transcribes the genetic information from the virus or retrotransposon from RNA into DNA, which can integrate into the host genome. ... Genera Alpharetrovirus Betaretrovirus Gammaretrovirus Deltaretrovirus Epsilonretrovirus Lentivirus Spumavirus A retrovirus is any virus belonging to the viral family Retroviridae. ...

In 1972, Walter Fiers and his team at the Laboratory of Molecular Biology of the University of Ghent (Ghent, Belgium) were the first to determine the sequence of a gene: the gene for Bacteriophage MS2 coat protein.^[11] Richard J. Roberts and Phillip Sharp discovered in 1977 that genes can be split into segments. This leads to the idea that one gene can make several proteins. Recently (as of 2003-2006), biological results let the notion of gene appear more slippery. In particular, genes do not seem to sit side by side on DNA like discrete beads. Instead, regions of the DNA producing distinct proteins may overlap, so that the idea emerges that "genes are one long continuum".^[1] Year 1972 (MCMLXXII) was a leap year starting on Saturday (link will display full calendar) of the Gregorian calendar. ... Walter Fiers was born in Ieper (Belgium) in 1931. ... Ghent University (in Dutch, Universiteit Gent, abbreviated UGent) is one of the two large Flemish universities. ... This article is about the Belgian city. ... The bacteriophage MS2 or Bacillus phage M2 (Caudovirales, Podoviridae) infects Bacillus subtilis. ... Richard J. Roberts (b. ... Phillip Allen Sharp (born June 6, 1944), U.S. geneticist and molecular biologist; co-discovered gene splicing; shared the 1993 Nobel Prize in Physiology or Medicine with Richard J. Roberts for the discovery that genes in eukaryotes are not contiguous strings but contain introns, and that the splicing of messenger... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: βίος, bio, life; and λόγος, logos, knowledge), also referred to as the biological sciences, is the study of living organisms utilizing the scientific method. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Look up Region in Wiktionary, the free dictionary. ... Look up continuum in Wiktionary, the free dictionary. ...

Mendelian inheritance and classical genetics

Main articles: Mendelian inheritance and Classical genetics

Darwin used the term Gemmule to describe a microscopic unit of inheritance, and what would later become known as Chromosomes had been observed separating out during cell division by Wilhelm Hofmeister as early as 1848. The idea that chromosomes were the carriers of inheritance was expressed in 1883 by Wilhelm Roux. The modern conception of the gene originated with work by Gregor Mendel, a 19th century Augustinian monk who systematically studied heredity in pea plants. Mendel's work was the first to illustrate particulate inheritance, or the theory that inherited traits are passed from one generation to the next in discrete units that interact in well-defined ways. Danish botanist Wilhelm Johannsen coined the word "gene" in 1909 to describe these fundamental physical and functional units of heredity,^[12] while the related word genetics was first used by William Bateson in 1905.^[10] The word was derived from Hugo De Vries' 1889 term pangen for the same concept ^[9], itself a derivative of the word pangenesis coined by Darwin (1868).^[13] The word pangenesis is made from the Greek words pan (a prefix meaning "whole", "encompassing") and genesis ("birth") or genos ("origin"). Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent organisms to their children; it underlies much of genetics. ... Classical genetics consists of the techniques and methodologies of genetics that predate the advent of molecular biology. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Wilhelm Friedrich Benedikt Hofmeister (18 May 1824 to 12 January 1877) was a German self-taught botanist. ... Wilhelm Roux (June 9, 1850–September 15, 1924) was a German zoologist and experimental embryologist. ... “Mendel” redirects here. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... The Augustinians, named after Saint Augustine of Hippo (died AD 430), are several Roman Catholic monastic orders and congregations of both men and women living according to a guide to religious life known as the Rule of Saint Augustine. ... Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent organisms to their children; it underlies much of genetics. ... Botany is the scientific study of plant life. ... Wilhelm Ludvig Johannsen (February 3, 1857 - November 11, 1927) was a Danish botanist. ... This article is about the general scientific term. ... William Bateson. ... For other uses, see 1905 (disambiguation). ... Hugo Marie de Vries (16th February 1848-21st May 1935), a Dutch biologist, was one of three men - see also Carl Correns and Erich von Tschermak - who in 1900 rediscovered Gregor Mendels work on genetics. ... Pangenesis was Charles Darwins hypothetical mechanism for heredity. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ...

According to the theory of Mendelian inheritance, variations in phenotype - the observable physical and behavioral characteristics of an organism - are due to variations in genotype, or the organism's particular set of genes, each of which specifies a particular trait. Different genes for the same trait, which give rise to different phenotypes, are known as alleles. Organisms such as the pea plants Mendel worked on, along with many plants and animals, have two alleles for each trait, one inherited from each parent. Alleles may be dominant or recessive; dominant alleles give rise to their corresponding phenotypes when paired with any other allele for the same trait, while recessive alleles give rise to their corresponding phenotype only when paired with another copy of the same allele. For example, if the allele specifying tall stems in pea plants is dominant over the allele specifying short stems, then pea plants that inherit one tall allele from one parent and one short allele from the other parent will also have tall stems. Mendel's work found that alleles assort independently in the production of gametes, or germ cells, ensuring variation in the next generation. Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... This article does not cite any references or sources. ... For the hard rock band, see Allele (band). ... In genetics, the term dominant gene refers to the allele that causes a phenotype that is seen in a heterozygous genotype. ... It has been suggested that this article or section be merged into Dominance relationship. ... A gamete (from Ancient Greek γαμετης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. ... A germ cell is part of the germline and is involved in the reproduction of organisms. ...

Prior to Mendel's work, the dominant theory of heredity was one of blending inheritance, which proposes that the traits of the parents blend or mix in a smooth, continuous gradient in the offspring. Although Mendel's work was largely unrecognized after its first publication in 1866, it was rediscovered in 1900 by three European scientists, Hugo de Vries, Carl Correns, and Erich von Tschermak, who had reached similar conclusions from their own research. However, these scientists were not yet aware of the identity of the 'discrete units' on which genetic material resides. Gregor Johann Mendel In Darwins time, biologists held to the theory of blending inheritance -- an offspring was an average of its parents. ... Hugo Marie de Vries (16th February 1848-21st May 1935), a Dutch biologist, was one of three men - see also Carl Correns and Erich von Tschermak - who in 1900 rediscovered Gregor Mendels work on genetics. ... Carl Erich Correns (September 10, 1864, in Munich - February 14, 1933) was a German botanist and geneticist, who is notable primarily for his independent discovery of the principles of heredity, and for his rediscovery of Gregor Mendels earlier paper on that subject, which he achieved simultaneously but independent of... Erich Tschermak-Seysenegg Erich von Tschermak-Seysenegg (November 15, 1871 – October 11, 1962) was an Austrian agronomist. ...

A series of subsequent discoveries led to the realization decades later that chromosomes within cells are the carriers of genetic material, and that they are made of DNA (deoxyribonucleic acid), a polymeric molecule found in all cells on which the 'discrete units' of Mendelian inheritance are encoded. The modern study of genetics at the level of DNA is known as molecular genetics and the synthesis of molecular genetics with traditional Darwinian evolution is known as the modern evolutionary synthesis. Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... This article is about the general scientific term. ... Molecular genetics is the field of biology which studies the structure and function of genes at a molecular level. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... This article is about evolution in biology. ... The modern evolutionary synthesis refers to a set of ideas from several biological specialities that were brought together to form a unified theory of evolution accepted by the great majority of working biologists. ...

Physical definitions

The chemical structure of a four-base fragment of a DNA double helix.

The vast majority of living organisms encode their genes in long strands of DNA. DNA consists of a chain made from four types of nucleotide subunits: adenosine, cytidine, guanosine, and thymidine. Each nucleotide subunit consists of three components: a phosphate group, a deoxyribose sugar ring, and a nucleobase. Thus, nucleotides in DNA or RNA are typically called 'bases'; consequently they are commonly referred to simply by their purine or pyrimidine original base components adenine, cytosine, guanine, thymine. Adenine and guanine are purines and cytosine and thymine are pyrimidines. The most common form of DNA in a cell is in a double helix structure, in which two individual DNA strands twist around each other in a right-handed spiral. In this structure, the base pairing rules specify that guanine pairs with cytosine and adenine pairs with thymine (each pair contains one purine and one pyrimidine). The base pairing between guanine and cytosine forms three hydrogen bonds, while the base pairing between adenine and thymine forms two hydrogen bonds. The two strands in a double helix must therefore be complementary, that is, their bases must align such that the adenines of one strand are paired with the thymines of the other strand, and so on. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... Adenosine is a nucleoside composed of adenine attached to a ribose (ribofuranose) moiety via a β-N9-glycosidic bond. ... Cytidine is a molecule (known as a nucleoside) that is formed when cytosine is attached to a ribose ring (also known as a ribofuranose) via a β-N1-glycosidic bond. ... The chemical structure of Guanosine Guanosine is a nucleoside comprising guanine attached to a ribose (ribofuranose) ring via a β-N9-glycosidic bond. ... The chemical structure of deoxythymidine Thymidine (more precisely called deoxythymidine can also be labelled deoxyribosylthymine, and thymine deoxyriboside) is a chemical compound, more precisely a pyrimidine deoxynucleoside. ... A phosphate, in inorganic chemistry, is a salt of phosphoric acid. ... Deoxyribose Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ... Adenine Guanine Thymine Cytosine ... Purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. ... Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring [1]. It is isomeric with two other forms of diazine. ... The Double-Helix are an alien race in the Wing Commander science fiction series. ... In genetics, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ... Guanine is one of the five main nucleobases found in the nucleic acids DNA and RNA; the others being adenine, cytosine, thymine, and uracil. ... Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at... For the programming language Adenine, see Adenine (programming language). ... For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ...

Due to the chemical composition of the pentose residues of the bases, DNA strands have directionality. One end of a DNA polymer contains an exposed hydroxyl group on the deoxyribose, this is known as the 3' end of the molecule. The other end contains an exposed phosphate group, this is the 5' end. The directionality of DNA is vitally important to many cellular processes, since double helices are necessarily directional (a strand running 5'-3' pairs with a complementary strand running 3'-5') and processes such as DNA replication occur in only one direction. All nucleic acid synthesis in a cell occurs in the 5'-3' direction, because new monomers are added via a dehydration reaction that uses the exposed 3' hydroxyl as a nucleophile. // Hydroxyl group The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. ... Deoxyribose Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... A phosphate, in inorganic chemistry, is a salt of phosphoric acid. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... DNA replication. ... Dehydration (hypohydration) is the removal of water (hydro in ancient Greek) from an object. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ...

The expression of genes encoded in DNA begins by transcribing the gene into RNA, a second type of nucleic acid that is very similar to DNA, but whose monomers contain the sugar ribose rather than deoxyribose. RNA also contains the base uracil in place of thymine. RNA molecules are less stable than DNA and are typically single-stranded. Genes that encode proteins are composed of a series of three-nucleotide sequences called codons, which serve as the "words" in the genetic "language". The genetic code specifies the correspondence during protein translation between codons and amino acids. The genetic code is nearly the same for all known organisms. Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Left: An RNA strand, with its nitrogenous bases. ... Look up nucleic acid in Wiktionary, the free dictionary. ... Ribose Ribose, primarily seen as D-ribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ... Deoxyribose Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ... Uracil is a pyrimidine which is common and naturally occurring. ... For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... RNA codons. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... This article is about the class of chemicals. ...

RNA genes

In some cases, RNA is an intermediate product in the process of manufacturing proteins from genes. However, for other gene sequences, the RNA molecules are the actual functional products. For example, RNAs known as ribozymes are capable of enzymatic function, and miRNAs have a regulatory role. The DNA sequences from which such RNAs are transcribed are known as non-coding DNA, or RNA genes. Left: An RNA strand, with its nitrogenous bases. ... // A ribozyme (from ribonucleic acid enzyme, also called RNA enzyme or catalytic RNA) is an RNA molecule that catalyzes a chemical reaction. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... The stem-loop secondary structure of a pre-microRNA from Brassica oleracea. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the deve