Efficient way to solve genetics mcat questions?

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Jun 6, 2007
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For example if the question is all factor 8 gene mutations result in hemophilia, which of the following choices is false? (This is how I summarized the question).
Given the following info: hemophilia is a sex-linked disease, recessive, located on x-chromosome.
Answer choices are something like this and A & C are correct.

A. hemophiliac mothers have healthy sons
B.Healthy fathers have Hemophiliac sons
C.Healthy fathers have Hemophiliac daughters
D.hemophiliac fathers have healthy sons

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It might be helpful if you took a screen shot or smartphone image of the exact question and answer choices. You have likely missed something in the wording. For what it is worth:

A - Hemophiliac mothers have two X chromosomes with the mutation of interest if the disease is x-linked recessive. A father never contributes an "X" chromosome to his son (only a y); thus, a hemophiliac mother would be the only contributor of an X chromosome to her son, which would be diseased. All sons of a hemophiliac mother should have the mutation, and thus the disease.
B - You're being too vague. Yes, it is possible for some healthy fathers to have diseased sons as it depends entirely on the mother.
C - Healthy fathers will never have hemophiliac daughters if the disease is x-linked recessive.
D - Same as B - entirely based on mom.

Choice A will never happen (all sons get mutant X allele). Choice C will never happen (all daughters get normal X allele).