Gene = Genes are entities that parents pass to offspring during
reproduction. These entities encode information essential for the
construction and regulation of polypeptides, proteins and other
molecules that determine the growth and functioning of the
organism.
The word "gene" is shared by many disciplines, including classical
genetics, molecular genetics, evolutionary biology and population
genetics. Because each discipline models the biology of life
differently, the usage of the word gene varies between disciplines.
It may refer to either material or conceptual entities.
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 RNA 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 conditionas in "the gene for
obesity." Speaking more precisely, a biologist 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
geneor single genetic locusfully determine one's genetic
predisposition for obesity. These aspects of inheritancethe
interplay between genes and environment, the influence of many
genesappear to be the norm with regard to many and perhaps most
("complex" or "multifactoral") traits. The term phenotype refers to
the characteristics that result from this interplay (see
genotype-phenotype distinction).
