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In humans, generally “men are affected and women are carriers“ for two reasons. The first is the simple statistical fact that if the X-chromosomes is a population that carry a particular X-linked mutation at a frequency of 'f' (for example, 1%) then that will be the frequency that men are likely to express the mutation (since they have only one X), while women will express it at a frequency of f2 (for example 1% * 1% = %) since they have two X's and hence two chances to get the normal allele. Thus, X-linked mutations tend to be rare in women. The second reason for female rarity is that women who express the mutation must have two X chromosomes that carry the trait and they necessarily got one from their father, who would have also expressed the trait because he only had one X chromosome in the first place. If the trait lowers the probability of fathering a child or induces the father to only have children with women who aren't carriers (so as not to create daughters who are carriers rather than expressers and then only if no genetic screening is used) then women become even less likely to express the trait. #chromosomes #genetics #mutation #biology #XlinkedTraits #genotype #phenotype #KhanAcademy #XChromosome #NikolaysGeneticsLessons #geneticDisease #geneticDisorder #DNA #RNA #geneticsDisorders #homozygous #hemizygous #XChromosomeInheritance #dominantTrait #geneticDesease #XlinkedRecessive #AutosomalRecessive #GeneticsExamQuestionsSolutions #SexlinkedDominant #skewedXinactivation #Xlinked #GeneticExamQuestionsSolutions #Genetics101 #sexlinkedRecessive
