Mendelian Genetic problems

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

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Ph0BoLuS
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Mendelian Genetic problems

Post by Ph0BoLuS » Wed Jun 11, 2008 4:13 pm

My instructor gave me some problems to help study for the quiz on Monday, but i have no idea how to go about solving them..

1) In martians, Gene 1 is determining eye shape (A-star eyes; a- square eyes) and Gene 2 is coding for presence or absence of tail hairs (B-hairy tail; b-smooth tail). True- breed star eyed individual with smooth tail marries another true-breed square-eyed individual with hairy tail and all of their childred have star eyes and hairy tailes. If mendelian Genetics works on Mars,

a) which allele of each gene is dominiant, and which is recessive?

Would the dominant ones be A,B, and the recessive a,b

b) What are the genotype of the parents?

Would the mother be A/A b/b and the father a/a B/B

c) What combinations of genes and in what proportions do you expect in the resulting gametes in parents?

I don't know how to figure this one out.

2)Assume that D,E,F,G,H and I are genes on ifferent chromosomes. From the mating (parent A) DdeeFfGGHhIi * (parent B) DdEEFFGgHhii:

a) What is probability that one of the offspring will have the genotype DdEeFFGghhIi?

would this answer be 1/(2^7)?

b) What is the probability that one of the offspring will be heterozygous for each allele?

I'm lost on this one.

c) How many different kinds of gametes can be produced by each parent?

128?

3)A dominant allele of a gene "A" causes yellow color in rats. The dominant allele of another independent gene, "R", produces black coat color. When 2 dominant genes occur together (A-R-), they produce grey coat color. Rats of the double recessive genotype are cream colored.

a) What kind of gene interaction iss that?

Would this be incomplete dominance?

b)If a grey male and a yellow female mated and produced approx. 3/8 yellow, 3/8 grey, 1/8 cream, and 1/8 black, what were the genotypes of the parents?

I tried the punnet squares, but keep getting confused with it.

Any help would be greatly appreciated, Thanks in advance.

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mith
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Post by mith » Wed Jun 11, 2008 4:33 pm

1c. Since the genes are independent you can do a punnet for the eyes and a separate punnet for the tails.

Then make combos of them.

For example if
you got for eyes - All Star
and for tails - 1/2 Hairy; 1/2 Smooth
Then you'd get - 1/2 Star+Hairy; 1/2 Star+Smooth
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Ph0BoLuS
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Post by Ph0BoLuS » Wed Jun 11, 2008 4:43 pm

for the punnet squares I never know how many letters to use. So would it look like this? For the eyes.

| A | a |
--------------------
A |AA | Aa |
--------------------
a |Aa | aa |

Ph0BoLuS
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Post by Ph0BoLuS » Wed Jun 11, 2008 5:28 pm

For 3b I have in the punnet square on top is: A/R, A/r, a/R, and a/r. for the left side I have: a/r and A/r. I worked out the punnet square and it came out to the 3/8 yellow, 3/8 grey, 1/8 cream, and 1/8 black, but what do I put as the answer?

EDIT: Sorry for the double post.

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Post by Cat » Thu Jun 12, 2008 8:40 pm

I posted your answer here:

http://science-ed.fullsubject.com/1-on- ... t28.htm#96

P.S. Mith, what exactly are you crossing here?

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