If a man has the premutation allele (on the X chromosome) for Fragile X syndrome, what...

If a man has the premutation allele (on the X chromosome) for Fragile X syndrome, what is the probability that he will pass it on to his son?

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Expert Solution

Answer - The probability that he will pass on to his son is zero (0).

explanation -

As in the inheritance of sex chromosomes sons got a Y-chromosome from father and X-chromosoome from mother. Lets assume that the X-chromosome of father with permutation allele for fragile X-syndrome be represented by Xf while normal X chromosome be represnt as X.

The following cross may occur

Parent(P1) genotype Father, XfY X Mother, XX

Gamete genotype Xf Y X X

F1 offspring – Punnett square

XfX

daughter

Son

As shown with the punnett square, father always transmits its Y-chromosome to its son and as the permutation allele for fragile X-syndrome is located on X-chromosome. Thus, father can never inherit the the permutaion allele to his son.

Therefore, the probability that it will pass on to his son is zero (0).

gladiator answered 1 year ago

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