Multiple Choice
In a family where the father has hemophilia (an X-linked recessive disorder) and the mother is a carrier, what is the probability of their daughter having hemophilia?
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13. Mendelian Genetics
Sex-Linked Inheritance
Multiple Choice
In a family where the mother is a carrier for colorblindness and the father has normal vision, which of the following children will have normal vision?
A
A daughter who is a carrier
B
A son with normal vision
C
A daughter who is colorblind
D
A son who is colorblind
Verified step by step guidance1
Understand that colorblindness is a sex-linked recessive trait, located on the X chromosome. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
Identify the genetic makeup of the parents: The mother is a carrier, meaning she has one normal vision allele (X) and one colorblind allele (Xc). The father has normal vision, so his genotype is XY.
Determine the possible genotypes for the children: For daughters, they can inherit one X chromosome from each parent, resulting in either XX (normal vision) or XcX (carrier). For sons, they inherit the X chromosome from the mother and the Y chromosome from the father, resulting in either XY (normal vision) or XcY (colorblind).
Analyze the options: A daughter who is a carrier (XcX) will have normal vision because the normal allele is dominant. A daughter who is colorblind (XcXc) is not possible with these parents. A son with normal vision (XY) inherits the normal X from the mother. A son who is colorblind (XcY) inherits the colorblind X from the mother.
Conclude that the child with normal vision is the son with the genotype XY, as he inherits the normal vision X chromosome from his mother and the Y chromosome from his father.
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