Multiple Choice
Which types of inheritance are observed in the ABO blood group system of humans?
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2. Mendel's Laws of Inheritance
Sex-Linked Genes
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If Brian has a son who is color-blind, which of the following statements is most likely true regarding the inheritance of the color-blindness allele?
A
Brian must be color-blind himself.
B
Brian's wife is a carrier of the color-blindness allele.
C
Color-blindness is inherited as an autosomal dominant trait.
D
Brian's son inherited the allele from his father.
Verified step by step guidance1
Identify the mode of inheritance for color-blindness. Color-blindness is typically inherited as an X-linked recessive trait, meaning the gene responsible is located on the X chromosome.
Recall that males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). Since males have only one X chromosome, if they inherit the recessive allele for color-blindness on their X chromosome, they will express the trait.
Understand that a son inherits his X chromosome from his mother and his Y chromosome from his father. Therefore, the son’s X-linked traits come from the mother, not the father.
Analyze the implication: if Brian's son is color-blind, the son must have inherited the color-blindness allele on the X chromosome from his mother, meaning Brian's wife is likely a carrier of the color-blindness allele.
Conclude that Brian does not have to be color-blind himself because he passes his Y chromosome to his son, not the X chromosome carrying the color-blindness allele.
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