Question

based on the pedigree, which of the following is true?
○ individual ii - 1 is a carrier for dmd.
● if individuals ii - 4 and ii - 5 have a fourth child, there is a 50% chance that it will not have dmd.
○ individual ii - 3 has a genotype of x^dy
○ if individual iii - 1 marries an unaffected, non - carrier female, none of their offspring will have dmd.

Explanation:

1. Analyze each option:

• For the statement about II - 1 being a carrier for DMD, there is no clear indication from the pedigree that II - 1 is a carrier.
• For II - 4 and II - 5, if DMD is an X - linked recessive disorder (as suggested by the pattern in the pedigree where mostly males are affected and it is passed from mother to son), and II - 4 is affected (presumably has the mutant allele on his X - chromosome) and II - 5 is affected, their children's probabilities depend on the mode of inheritance. If it's X - linked recessive, when they have a child, there is a 50% chance of having an unaffected child (either a non - carrier daughter or an unaffected son depending on the sex - linked nature).
• For II - 3 having a genotype of \(X^{D}Y\), since II - 3 is affected, this is incorrect as \(X^{D}Y\) would be an unaffected male genotype for an X - linked recessive disorder.
• For III - 1, if he marries an unaffected non - carrier female, assuming DMD is X - linked recessive, since he is unaffected and the female has no mutant alleles, their offspring will not have DMD. But the option about II - 4 and II - 5 having a 50% chance of an unaffected child is also correct based on X - linked recessive inheritance analysis.

Answer:

If individuals II - 4 and II - 5 have a fourth child, there is a 50% chance that it will not have DMD; If individual III - 1 marries an unaffected, non - carrier female, none of their offspring will have DMD.