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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. [4] [5]
The changes that constitute acquired characteristics can have many manifestations and degrees of visibility, but they all have one thing in common. They change a facet of a living organism's function or structure after birth. For example: The muscles acquired by a bodybuilder through physical training and diet. The loss of a limb due to an injury.
A comparison of a mouse unable to produce leptin thus resulting in obesity (left) and a normal mouse (right). The ob/ob or obese mouse is a mutant mouse that eats excessively due to mutations in the gene responsible for the production of leptin and becomes profoundly obese.
Population genetics is the branch of evolutionary biology responsible for investigating processes that cause changes in allele and genotype frequencies in populations based upon Mendelian inheritance. [3] Four different forces can influence the frequencies: natural selection, mutation, gene flow (migration), and genetic drift. A population can ...
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]
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 ...
Risk factors are divided into three categories; genetic, environmental and complex factors (for example overweight). Genetic risk factors are associated with the permanent changes in the base pair sequence of human genome. In the last decade, many studies have been generated data regarding genetic basis of multifactorial diseases.
Genetic effects are broadly divided into two categories: additive and non-additive. Additive genetic effects occur where expression of more than one gene contributes to phenotype (or where alleles of a heterozygous gene both contribute), and the phenotypic expression of these gene(s) can be said to be the sum of these contributions.