BMAT 2021 Q25 - Biology

Hi guys, I am having trouble understanding the statement 3 being wrong. At the beginning I only considered autosomal recessive, then i corporated X-linked recessive but still confused because statement 1 and 2 seems wrong too. Any help?


this seems to be X-linked, individuals 1) and 4) would be hemizygous not heterozygous no?? To me these are two very different terms are they not?

Also individual 6) has 25% chance of being a carrier and thus heterozygous in my opinion

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Actually this is a tricky questions because both, autosomal recessive and X-linked recessive are possible so we must keep our options open.

Individuals 5 and 6, since both are healthy, must either be homozygous dominant or heterozygous. Based on the previous statements, we assume this is autosomal recessive, so the they both have 66% chance of being Aa and 33% of being AA (since they are healthy).