Gene

A chromosome and its packaged long strand of DNA unraveled. The DNA's base pairs encode genes, which provide functions. A human DNA can have up to 500 million base pairs with thousands of genes.

In biology, the word gene (Greek: γένος, génos;^[1] generation,^[2] or birth,^[1] or gender) has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA, that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes.^[3]^[4]^[5]^[6]

During gene expression, DNA is first copied into RNA. RNA can be directly functional or be the intermediate template for the synthesis of a protein.

The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype, that is specific to every given individual, within the gene pool of a population of a given species. The genotype, along with environmental and developmental factors, ultimately determines the phenotype of the individual. Most biological traits occur under the combined influence of polygenes (a set of different genes) and gene–environment interactions. Some genetic traits are instantly visible, such as eye color or the number of limbs, others are not, such as blood type, the risk for specific diseases, or the thousands of basic biochemical processes that constitute life.

A gene can acquire mutations in its sequence, leading to different variants, known as alleles, in the population. These alleles encode slightly different versions of a gene, which may cause different phenotypical traits.^[7] Genes evolve due to natural selection or survival of the fittest and genetic drift of the alleles.

The term gene was introduced by Danish botanist, plant physiologist, and geneticist Wilhelm Johannsen in 1909.^[8] It is inspired by the ancient Greek: γόνος, gonos, that means offspring and procreation.

^ ^a ^b "1909: The Word Gene Coined". genome.gov. Retrieved 8 March 2021. "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..."
^ Roth SC (July 2019). "What is genomic medicine?". Journal of the Medical Library Association. 107 (3). University Library System, University of Pittsburgh: 442–448. doi:10.5195/jmla.2019.604. PMC 6579593. PMID 31258451.
^ Cite error: The named reference mendgene2 was invoked but never defined (see the help page).
^ "What is a gene?: MedlinePlus Genetics". MedlinePlus. 17 September 2020. Retrieved 4 January 2021.
^ Hirsch ED (2002). The new dictionary of cultural literacy. Boston: Houghton Mifflin. ISBN 0-618-22647-8. OCLC 50166721.
^ "Studying Genes". nigms.nih.gov. Archived from the original on 17 January 2021. Retrieved 15 January 2021.
^ Elston RC, Satagopan JM, Sun S (2012). "Genetic terminology". Statistical Human Genetics. Methods in Molecular Biology. Vol. 850. Humana Press. pp. 1–9. doi:10.1007/978-1-61779-555-8_1. ISBN 978-1-61779-554-1. PMC 4450815. PMID 22307690.
^ Johannsen W (1909). Elemente der exakten Erblichkeitslehre [Elements of the exact theory of heredity] (in German). Jena, Germany: Gustav Fischer. p. 124. From p. 124: "Dieses "etwas" in den Gameten bezw. in der Zygote, ... – kurz, was wir eben Gene nennen wollen – bedingt sind." (This "something" in the gametes or in the zygote, which has crucial importance for the character of the organism, is usually called by the quite ambiguous term Anlagen [primordium, from the German word Anlage for "plan, arrangement; rough sketch"]. Many other terms have been suggested, mostly unfortunately in closer connection with certain hypothetical opinions. The word "pangene", which was introduced by Darwin, is perhaps used most frequently in place of Anlagen. However, the word "pangene" was not well chosen, as it is a compound word containing the roots pan (the neuter form of Πας all, every) and gen (from γί-γ(ε)ν-ομαι, to become). Only the meaning of this latter [i.e., gen] comes into consideration here; just the basic idea – [namely,] that a trait in the developing organism can be determined or is influenced by "something" in the gametes – should find expression. No hypothesis about the nature of this "something" should be postulated or supported by it. For that reason it seems simplest to use in isolation the last syllable gen from Darwin's well-known word, which alone is of interest to us, in order to replace, with it, the poor, ambiguous word Anlage. Thus we will say simply "gene" and "genes" for "pangene" and "pangenes". The word gene is completely free of any hypothesis; it expresses only the established fact that in any case many traits of the organism are determined by specific, separable, and thus independent "conditions", "foundations", "plans" – in short, precisely what we want to call genes.)

[jeans-1] "1909: The Word Gene Coined". genome.gov. Retrieved 8 March 2021. "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..."

[Roth_p.-2] Roth SC (July 2019). "What is genomic medicine?". Journal of the Medical Library Association. 107 (3). University Library System, University of Pittsburgh: 442–448. doi:10.5195/jmla.2019.604. PMC 6579593. PMID 31258451.

[mendgene2-3] Cite error: The named reference mendgene2 was invoked but never defined (see the help page).

[MedlinePlus_2020-4] "What is a gene?: MedlinePlus Genetics". MedlinePlus. 17 September 2020. Retrieved 4 January 2021.

[Hirsch_2002_p.-5] Hirsch ED (2002). The new dictionary of cultural literacy. Boston: Houghton Mifflin. ISBN 0-618-22647-8. OCLC 50166721.

[6] "Studying Genes". nigms.nih.gov. Archived from the original on 17 January 2021. Retrieved 15 January 2021.

[7] Elston RC, Satagopan JM, Sun S (2012). "Genetic terminology". Statistical Human Genetics. Methods in Molecular Biology. Vol. 850. Humana Press. pp. 1–9. doi:10.1007/978-1-61779-555-8_1. ISBN 978-1-61779-554-1. PMC 4450815. PMID 22307690.

[Johannsen-8] Johannsen W (1909). Elemente der exakten Erblichkeitslehre [Elements of the exact theory of heredity] (in German). Jena, Germany: Gustav Fischer. p. 124. From p. 124: "Dieses "etwas" in den Gameten bezw. in der Zygote, ... – kurz, was wir eben Gene nennen wollen – bedingt sind." (This "something" in the gametes or in the zygote, which has crucial importance for the character of the organism, is usually called by the quite ambiguous term Anlagen [primordium, from the German word Anlage for "plan, arrangement; rough sketch"]. Many other terms have been suggested, mostly unfortunately in closer connection with certain hypothetical opinions. The word "pangene", which was introduced by Darwin, is perhaps used most frequently in place of Anlagen. However, the word "pangene" was not well chosen, as it is a compound word containing the roots pan (the neuter form of Πας all, every) and gen (from γί-γ(ε)ν-ομαι, to become). Only the meaning of this latter [i.e., gen] comes into consideration here; just the basic idea – [namely,] that a trait in the developing organism can be determined or is influenced by "something" in the gametes – should find expression. No hypothesis about the nature of this "something" should be postulated or supported by it. For that reason it seems simplest to use in isolation the last syllable gen from Darwin's well-known word, which alone is of interest to us, in order to replace, with it, the poor, ambiguous word Anlage. Thus we will say simply "gene" and "genes" for "pangene" and "pangenes". The word gene is completely free of any hypothesis; it expresses only the established fact that in any case many traits of the organism are determined by specific, separable, and thus independent "conditions", "foundations", "plans" – in short, precisely what we want to call genes.)

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