Sex-Linked Inheritance quiz #4 Flashcards
Sex-Linked Inheritance quiz #4
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How can a female be affected by an X-linked recessive disorder, and what must be true about her parents' genotypes?
A female can be affected by an X-linked recessive disorder only if she inherits two recessive alleles, one from each parent. This means her father must be affected (having the recessive allele on his only X chromosome), and her mother must be either affected or a carrier (heterozygous for the trait). What is the main difference between the X and Y chromosomes in terms of gene content?
The X chromosome is much larger and contains about 1100 genes, while the Y chromosome is smaller and contains only about 100 genes. How do males and females differ in the number of alleles they have for X-linked genes?
Females have two alleles for each X-linked gene (one on each X chromosome), while males have only one allele for each X-linked gene (on their single X chromosome). Why are males more likely to express X-linked recessive disorders than females?
Males only have one X chromosome, so a single recessive allele on that chromosome will result in the disorder, whereas females need two recessive alleles to be affected. What must be true about a female's parents for her to be affected by an X-linked recessive disorder?
Her father must be affected (having the recessive allele on his only X chromosome), and her mother must be either affected or a carrier (heterozygous for the trait). In a Punnett square for X-linked inheritance, what is the probability of having a male or female offspring?
There is a 50% chance of having a female (XX) and a 50% chance of having a male (XY) with each fertilization event. What is hemophilia and how is it inherited?
Hemophilia is an X-linked recessive disorder characterized by abnormal blood clotting, and it is inherited when an individual receives the recessive allele on the X chromosome. In X-linked recessive pedigrees, what pattern is typically observed regarding affected individuals?
More males are affected than females, and affected females are rare and only occur if the father is affected and the mother is at least a carrier. What happens to the sons of a female who is affected by an X-linked recessive disorder?
All sons of an affected female will be affected by the disorder. How can you quickly identify an X-linked recessive disorder in a pedigree chart?
Look for a pattern where significantly more males are affected than females, and check if affected females have affected fathers and carrier or affected mothers.
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