Grad Print Ca Table Map Genetics: A Conceptual Approach 6th Edton MHE/Freeman An
ID: 195389 • Letter: G
Question
Grad Print Ca Table Map Genetics: A Conceptual Approach 6th Edton MHE/Freeman An X-inked recessive gene causes red-green color blindness in humans. Suppose John and Cathy have normal color vision. After 10 years of marriage to John, Cathy has a color-blind son. John filed for divorce, claiming that he is not the birth to a color-blind daughter and r of at least one of the children. Which of the following statements describes John's paternity claim? O He cannot be the father of either child O He cannot be the father of Cathy's daughter. O He couid be the father of both children O He cannot be the father of Cathy's son HintExplanation / Answer
Assuming that the color-blindness is a recessive trait, the color-blind daughter must be homozygous recessive. If the color-blindness trait here is not X-linked, then John has no justification, because both John and Cathy could be carriers. If the color-blindness is the X-linked red-green color-blindess, then John has grounds for suspicion. Normally, their daughter would have inherited John’s X chromosome. Since John is not color-blind, he could not have transmitted a color-blind X chromosome to the daughter. The alternative possibility is that the daughter is XO, having inherited a recessive color-blind allele from her mother and no sex chromosome from her father. In that case, the daughter would have Turner syndrome. If Cathy had a color-blind son, then John would have no grounds for suspicion. The son would have inherited John’s Y chromosome and the color-blind X chromosome from Cathy.
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