PATHOLOGY MCQ
GENETICS AND DISEASE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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each parent must be colorblind
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each parent must have the dominant allele for colorblindness
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each parent must have the recessive allele for colorblindness
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each parent must have two codominant alleles for colorblindness
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Detailed explanation-1: -Females have 2 X chromosomes, one from their mother and one from their father. To have red-green color blindness, both X chromosomes would need to have the gene for red-green color blindness.
Detailed explanation-2: -The recessive chromosome is represented as Xr. Since males have only one X-chromosome, if this chromosome has the red-green color blind allele, the males will have the color perception defect. Females have 2 X-chromosomes. Both X-chromosomes must carry the mutant allele for the females to be color blind.
Detailed explanation-3: -This means that girls need to inherit two copies of the colorblindness gene to be colorblind–one from each parent. Daughters with colorblind fathers will always be carriers of the colorblindness gene. They can be colorblind themselves if they also inherit a copy of the colorblindness gene from their mother.
Detailed explanation-4: -This is because the genes for the color vision cone light-sensitive proteins are on the X chromosome, of which males have one and females have two.
Detailed explanation-5: -Let (Xc) represent the recessive allele that causes colorblindness and (X+) represent the normal dominant allele. Females that are X+X+ or X+Xc have normal color vision, while XcXc females are colorblind.