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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 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 ...
[11] [9] [4] It can also provide information about estrogen status when there are questions of whether FHA or PCOS should be the diagnosis. [9] Withdrawal bleeding following the progestin challenge indicates sufficient levels of E2 for endometrial thickening, and that the amenorrhea is a result of anovulation and progesterone deficiency. [ 4 ]
Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents.
Genetic load may increase when deleterious mutations, migration, inbreeding, or outcrossing lower mean fitness. Genetic load may also increase when beneficial mutations increase the maximum fitness against which other mutations are compared; this is known as the substitutional load or cost of selection.
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 ...
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.
For example, it is incorrect to say that since the heritability of personality traits is about 0.6, that means that 60% of your personality is inherited from your parents and 40% comes from the environment. In addition, heritability can change without any genetic change occurring, such as when the environment starts contributing to more variation.