Genetic Pedigree Multiple Choice Quiz – 3

Fun pedigree! Do any of these common modes of inheritance explain this pedigree? If so, which is most likely?
X-linked recessive
Yes, this works. The right hand side has the classic skips a generation with only males affected. The one that might throw you is the affected female at the end but as it is X recessive, her mother need only be a carrier, which is possible.
Non-genetic
Always an option, of course, however, there is an explanation for this pedigree that does suggest an inheritance pattern.
Y-linked
The final child is a female – assuming she is XX then it can not be Y linked.
Mitochondrial
nope, no suggestion of maternal inheritance
Autosomal Dominant
This isn’t really an option due to the skipped generations here.
Multi-gene disorder
Possible, but there is a simpler answer.
The affected female at the bottom of the pedigree comes to you for advice about her future children. What would you tell her?
Your male children would have the disorder, your female children would be unaffected carriers
Your male children would have a 50/50 chance of being affected by the disorder, your female children would have a 50/50 chance of being carriers.
assuming you worked out that this is an X-linked recessive disorder. An affected female in X-linked conditions has two mutated X copies.
Your male and your female children would have the disorder.
Assuming the father was unaffected then the female offspring would get one mutant X and one wild type X and would be unaffected.
Your male children will be unaffected, your female children will be unaffected carriers
Nope, if this is X linked then it is guaranteed that an affected X chromosome will go to every one of her male children. They will be affected.
Your male children would have the disorder, your female children would be unaffected and would not be carriers
female children would get one mutated X and therefore would be carriers.
The female at top right remarried (hence connected to two males). The had a daughter. What is that daughter’s genotype?
XX
there is no reason to think that the mother is a carrier and the father is unaffected, therefore XX is the most likely genotype here
Xx
xx
XY
xY
XXX

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