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Genetics Questions

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Genetics Questions

Postby ecstyle » Tue Sep 18, 2007 8:29 am

I am new to studying genetics and not entirely familiar with the concept yet and ran into a few troublesome questions.

1. A woman with dimples marries a gentleman who lacks dimples. the woman's father lacks dimples but her mother has them. what percent of the newlywed's children can be expected to have dimples?

2. Two "lefties" marry. what percent of their offspring can be expected to be left-handed?

3. Two normally pigmented adults, each having an albino child from a previous marriage, get marry. what proportion of their children can be expected to be albino? what proportion of their children should be normally pigmented carriers of albinism?

1. For this question, do we assume the woman's genotype is DD or Dd (D = dominant gene for dimples, d= recessive gene for lacking dimple) and the man to be dd? Since the woman's father lacks dimples, she has to be Dd? so the percentage is Dd x dd ? and the answer is 50% ????

2. Are we assuming that man and woman have recessive genes ...
so it would be rr x rr and the answer is 100%?

3. Would it be Aa x Aa (where A = normal pigment and a = albino) and the answer would be 75% for normal pigment and 25% for albino?

Any one that agrees or disagree and provide some input would be greatly appreciated.

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Postby Jammerz » Wed Sep 19, 2007 4:13 am

1. Your reasoning and answer are correct.
2. Also correct.
3. Close... your phenotypic ratios are correct, but the question asks how many of the children will be carriers (ie, heterozygous) and how many will be albino. You are correct in saying that 25% will be albino. And 75% will be phenotypically normal. But how many will be carriers of the gene (aka heterozygous)?

It's always nice when someone shows their thought process and attempts at answering questions!
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