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Like many other medical conditions, obesity is the result of an interplay between environmental and genetic factors. [2] [3] Studies have identified variants in several genes that may contribute to weight gain and body fat distribution; although, only in a few cases are genes the primary cause of obesity.
Set point theory does not on its own explain why body mass index for humans, measured as a proxy for fat, tends to change with increasing age or why obesity levels in a population vary depending on socioeconomic or environmental factors (or why weight tends to change for an individual when socioeconomic status and environment change). [4]
The absolute fitness of a genotype is defined as the proportional change in the abundance of that genotype over one generation attributable to selection. For example, if n ( t ) {\displaystyle n(t)} is the abundance of a genotype in generation t {\displaystyle t} in an infinitely large population (so that there is no genetic drift ), and ...
Genetic variation can be identified at many levels. Identifying genetic variation is possible from observations of phenotypic variation in either quantitative traits (traits that vary continuously and are coded for by many genes, e.g., leg length in dogs) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes, e.g., white, pink, or red petal color ...
The classic example of such a genetic effect is the presence of mutations in the leptin gene. [ 29 ] An important unanswered question is whether such rare variants exist because of chance mutations, population founder events and maintenance by processes such as drift, or whether there is any selective advantage involved in their maintenance and ...
Both environmental and genetic factors often impact the variation in expression. Human height is a continuous trait meaning that there is a wide range of heights. There are an estimated 50 genes that affect the height of a human. Environmental factors, like nutrition, also play a role in a human's height.
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Heredity of phenotypic traits: a father and son with prominent ears and crowns. DNA structure. Bases are in the centre, surrounded by phosphate–sugar chains in a double helix. In humans, eye color is an example of an inherited characteristic: an individual might inherit the "brown-eye trait" from one of the parents. [1]