Bmat 2021 biology q 25

answer: E
can someone explain why 3 is wrong? thanks

With 5 and 6 we know they have a brother that has the condition (so the parents must be heterozygous)
Drawing out a punnett square we would have the ratio of 1:2:1 in terms of outcome (homo dom: hetero: homo recessive)
We know they are not homozygous recessive from the diagram
so we focus on what they could be - from the ratio we take the 1:2 (homo dom: hetero) there is approx. 66% chance they are heterozygous for this condition

I think this is how that question works


I’m confused with the fact that males genotypes being heterozygous, from what I know males genotypes are considered to be hemizygous, rather than hetero or homozygous.
So, according to this question, can we consider males genotypes to be heterozygous for uninfected person, then? Plz clarify this for me.

here is how you can differentiate between these two terms:
heterozygous: Heterozygous refers to a condition in which an individual has two different alleles (gene variants) at a specific genetic locus (location on a chromosome) for a particular gene. Aa or bB
hemizygous: Hemizygosity typically occurs in males for genes located on the X or Y chromosome. For example, males have only one X chromosome (XY), so they are hemizygous for X-linked genes. If a gene is located on the Y chromosome, it is hemizygous in males. Hemizygous individuals may express the alleles present on their single copy of the gene without the masking effects of a second allele (as in the case of heterozygotes).\

in this question we are not dealing with a sex-linked disease, it is an autosomal pattern. that is why we can call this a normal herezygous person male or female.


Ohh that’s right!!
I totally missed that point!!
Thank you so much!!

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