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Hemophilia A: The classic hemophilia resulting from a deficiency of factor Viii. It is an inherited disorder of blood coagulation characterized by a permanent tendency to hemorrhage.

Genetics of Organisms- Concept

JoVE 10557

Mendelian Genetics

Evolution is caused by changes in the genetic composition of populations. In the field of population genetics, scientists model this process as changes in the frequency of alleles at individual genetic loci. This simple representation of how evolution occurs dates to Gregor Mendel’s analysis of trait inheritance patterns in pea plants, first presented in 1865.…

 Lab Bio

X-linked Traits

JoVE 10980

In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be masked by the presence of a normal allele on the second X. In contrast, a mutation on the X chromosome in males more often causes observable biological defects, as there is no normal X to compensate. Trait variations arising from mutations on the X chromosome are called “X-linked”. One well-studied example of an X-linked trait is color blindness. When a mutation occurs in the genes responsible for red and green color vision in the photoreceptors of the retina, color blindness may occur. While this recessive mutation can cause females to be color blind, they must possess two mutated X chromosomes. Color blindness is much more common in males, who only have one X chromosome and therefore no second copy to potentially compensate for the mutation. Color blindness is passed from mother to son; a mutated X will be passed from the mother to half of her sons, who receive a Y from their father. Meanwhile, colorblind males will pass on the allele for color blindness to all of their daughters, who will be either carriers or color blind, depending on the maternal allele received. Occasionally, this type of X-linked mutation can also arise by spontaneous mutation and not as the result of inheritance from mother or

 Core: Classical and Modern Genetics
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