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NBME 24 Answers

nbme24/Block 1/Question#5

The 35-year-old woman indicated by the arrow has a ...

X-linked recessive

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 +4  upvote downvote
submitted by stars and more(4),

X linked recessive there can never be any Male to Male transfer since the male offspring gets Y from father. the pedigree shows Male to Male transmission so this cannot be X linked recessive

 +3  upvote downvote
submitted by monoclonal(6),

The point here is, they are asking us to eliminate the only answer that is not possible. I got it wrong. read well fellas

 +2  upvote downvote
submitted by trazabone(6),

My understanding is that if parents are unrelated by blood to those affected, we assume that they are not carriers (in the recessive case). Therefore, if we have a male father affected with x-linked recessive married to a non-carrier, there's no way any of his offspring would be affected.

"If one parent is not a carrier, then a child can only inherit a disease allele from the other parent. In these problems, we can assume that any individual marrying into the family is not a carrier." https://www.cs.cmu.edu/~genetics/units/instructions/instructions-CP.pdf

linwanrun1357  If we assume that they are not carriers (in the recessive case) Then how came it can be AR?!! +