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: only the exons encode the protein. This diagram labels a region of only 40 or so bases as a gene. In reality many genes are much larger.
Genes are material entities that parents pass to offspring during reproduction. These entities encode information essential for the construction and regulation of polypeptides, proteins and other moleculeIn science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. A molecule consists of multiple atoms joined by shared pairs of electrons in a covalent bond''. It may consist of atoms that determine the growth and functioning of the organismIn biology and ecology, an organism is a living being. The origin of life and the relationships between its major lineages are controversial. Two main grades may be distinguished, the prokaryotes and eukaryotes. The prokaryotes are generally considered to.
The word "gene" is shared by many disciplines, including classical geneticsClassical genetics consists of the techniques and methodologies of genetics that predate the advent of molecular biology. A key disocvery of classical genetics in eukaryotes, was genetic linkage. The observation that some genes do not segregate independen, molecular geneticsMolecular genetics is the field of biology which studies the structure and function of genes at a molecular level. Molecular genetics employs the methods of genetics and molecular biology. It is so-called to differentiate it from other sub fields of genet, evolutionary biologyEvolutionary biology is a subfield of biology concerned with the origin and descent of species, as well as their change over time, i. their evolution. One who studies evolutionary biology is known as an evolutionary biologist or less frequently evolutioni and population geneticsPopulation genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation and migration. It also takes account of population subdivision and pop. Because each disciplineDiscipline is any training intended to produce a specific character or pattern of behaviour, especially training that produces moral or mental development in a particular direction. Forms of discipline Control obtained by enforcing compliance or order. models the biology of life differently, the material entity that supports the gene in one discipline is not the same as in the other.
Following the discovery that DNA is the genetic material, and with the growth of biotechnology and the project to sequence the human genome, the common usage of the word "gene" has increasingly reflected its meaning in molecular biology. In the molecular-biological sense, genes are the segments of DNA which cells transcribe into RNAs and translate, at least in part, into proteins.
In common speech, "gene" is often used to refer to the hereditary cause of a trait, disease or condition—as in "the gene for obesity." A biologist, in contrast, might refer to an allele or a mutation that has been implicated in or is associated with obesity. This is because biologists know that many factors other than genes decide whether a person is obese or not: prenatal environment, upbringing, culture and the availability of food, for example.
Moreover, it is very unlikely that variations within a single gene—or single genetic locus—determine one's genetic predisposition for obesity. These aspects of inheritance—the interplay between genes and environment, the influence of many genes—appear to be the norm with regard to many and perhaps most ("multifactoral") traits. The term phenotype refers to the characteristics that result from this interplay (see genotype-phenotype distinction).
