Originally Posted by
tonioyantao
got it from wikipedia.
"Inbreeding
Incest that results in offspring is a form of close inbreeding (reproduction between two individuals with a common ancestor). Inbreeding leads to a higher probability of congenital birth defects because it increases that proportion of zygotes that are homozygous, in particular for deleterious recessive alleles that produce such disorders.[50] Because most such alleles are rare in populations, it is unlikely that two unrelated marriage partners will both be heterozygous carriers. However, because close relatives share a large fraction of their alleles (e.g., 50% for siblings or parent/offspring combinations, 25% for first cousins), the probability that any such rare deleterious allele present in the common ancestor will be inherited from both related parents is increased dramatically with respect to non-inbred couples. Contrary to common belief, inbreeding does not in itself alter allele frequencies, but rather increases the relative proportion of homozygotes to heterozygotes. However, because the increased proportion of deleterious homozygotes exposes the allele to natural selection, in the long run its frequency decreases more rapidly in inbred population. In the short term, incestuous reproduction is expected to produce increases in spontaneous abortions of zygotes, perinatal deaths, and postnatal offspring with birth defects.[51] HM Slatis [52] showed a significant delay in time to first pregnancy in first-cousin marriages as compared with unrelated individuals in the same population. A 1994 study found a mean excess mortality with inbreeding among first cousins of 4.4%.[53] A study of 29 offspring resulting from brother-sister or father-daughter incest found that 20 had congenital abnormalities, including four directly attributable to autosomal recessive alleles.[54]"
thou cousin to cousin marriage is not that rare it is considered taboo in our society.
but common in the middle east. also in India and pakistan. where arrange marriage is a common practice. in the uk alone. there is a law being passed to make it illegal because of a high number of children being born with defects from pakistani mothers with husbands that are also a close relative. i think it was on cnn 2 years ago.
but still lain gihapon kay first degree..
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