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Apr 6, 2010
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i'm having difficulty seeing the gametes that form in each parent.


The question. Answer: D


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Hey, I remember this. Lemme edit it as I actually got it right.

So the female is X(Ff) and X(Ee), because the male shows a mixture of recessive and dominant. The male is X(FE) because those are the only X he can display. Y is obviously ignored here.
So males can be: X(FE) X(Fe) X(fE) X(fe), all of which is shown. There are three recombs, the ones that aren't X(FE).
Females can only display the dominant phenotype because the male contributes X(FE), any X(fe) would get washed out.

=== Let's analyze what I did because I just memorized the answer in TPR ===
You're told both animals are dominant expressions. You look at the chart and see out of eveyrthing, the female still has dominant. Therefore if there were recessive options--which there are--they are ignored. It is either being masked, or pure dominant.
But...the males show recessive traits. They can only inherit an X from their mother. So the mother in this case, she ain't homozygous X! So she's probably X(Ff, Ee). This explains the rest of what I wrote here.

A) I have no idea what this means.
B) I have no idea what this means as well. Do they mean FE or fe ? In that case, then no, because X(fe) is an option.
C) I have no idea what this means.
D) This is the most applicable out of what I said?

Genetics is a really weak chapter for me. Thanks for reminding me I should go over it bro.
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Quick question: Is this from TPRH science workbook? B/c if so, I need to get started on that.
Quick question: Is this from TPRH science workbook? B/c if so, I need to get started on that.

IIRC; it's in-chapter. And you should be a good way through if you're taking on 4/28; I did like 50+ passages yesterday through physics-ochem!
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You need to consider what combinations could give you something like this (oftentimes it's easiest to consider each trait separately). The female is to be heterozygous for the dominant traits because there is no other way for the males to get the recessive traits, and the father only has one X chromosome and is normal/extra toed so he's dominant.

Given the fact that the male is dominant for both traits, it doesn't matter for female offspring what the recombination frequency looks like- no matter what they get from mom, they get and F and an E from dad. Thus 100% of them have normal hair and extra toes.

So, in the absence of recombination, half the males would be dominant for both traits and half recessive for both traits. That crosses B off the list.

A you cannot even evaluate from the data because you aren't given progeny genotypes. IT would probably be true IRL because a female child could get a recombinant genotype from mom but not dad, but it's not true as per the data.

C is wrong because male X chromosomes don't recombine since they're paired with the Y chromosome, but female X chromosomes do.

So D is our answer- remember that the recombinant phenotypes come from the mother. We can infer that there are recombinant female genotypes because the males are getting recombinant X chromosomes from the mom.
thanks you guys were very helpful

if anybody needs more explanation:


what really confused me was figuring out that FE and fe were linked together.
LOL I'm an idiot, I once again wrote a post that covered everything that pfaction had answered well because I'm too loopy to read the previous posts.
Yeah just remember it's X(FE) X(fe) because I'm also loopy after taking AAMC5 today. Sorry about that.
Since X(FE) and X(fe), recombination can occur to make X(Fe) and X(fE).
They're not linked otherwise it couldn't occur. Law of segregetion and indep assortment means F or f can go with e or E, which it does.
I think you understand but are just off on terminology here, but they are linked. If they weren't linked and independently assorted (usually this means they are on different chromosomes, but in this case it would mean they are far apart on the same chromosome), you would be getting FE, Fe, fE, and fe in equal proportions. But instead because they're close together on the same chromosome, you're getting almost only FE and fe. The Fe and fE X chromosomes are the result of recombination.

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