A phenotypically normal couple seeks genetic counseling because the man's karyotype showed that his chromosomes had a reciprocal translocation between chromosomes 4 and 12. Because the translocation is reciprocal there was no genetic information lost and he is healthy; however, he and his wife want to know the probability that his sperm cells will be abnormal. Which fraction of his sperm cells is predicted to carry at least one chromosome with a translocation?

Question

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In cases of reciprocal translocation, during meiosis, chromosomes align in such a way that three out of the four resulting gametes will have chromosomes involved in the translocation. This results in 3/4 of the sperm carrying at least one chromosome with a translocation, while only 1/4 will have both chromosomes 4 and 12 unaffected.

A Phenotypically Normal Couple Seeks Genetic Counseling Because the Man's