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Genetics Problems... Friends i need ur help

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

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Genetics Problems... Friends i need ur help

Postby hemu0912 » Wed Jul 15, 2009 4:06 am

Friends i really need ur help... i'm stuck with genetics problems n want to learn how to do it so plz....friends do it n explain me in detail how u did.
#1. The presence of dominant alleles at two different loci (A--B--) in poultry results in a walnut comb. Pea comb is produced by the genotype aaB--, rose comb by A--bb, and single comb by aabb. If you were given a rooster with a walnut comb, known to be heterozygous for both genes, and a rose-comb hen from a true-breeding strain, what cross or crosses, and how many generations, would it take to obtain true-breeding peacomb poultry?

#2The autosomal genes Curly (C) and Plum (P) in Drosophila are independently segregating, phenotypically dominant mutations that are homozygous lethals. In other words, they have a distinct phenotype as heterozygotes but are lethal as homozygous dominants. When Curly and Plum are separately crossed to wild-type flies and the F1 mutant progeny are intercrossed, what will the resulting phenotypic ratio be?

#3 Many matings between a dark, short-haired dog and a dark, longhaired dog yield the following progeny:
36 dark, short
39 dark, long
11 albino, short
13 albino, long
Explain these results.

#9 For the following cross,
Aa Bb cc Dd x Aa bb CC Dd
what is the chance of obtaining an individual who:
a. shows all dominant traits?
b. shows all recessive traits?
c. is phenotypically like the second party?
d. is genotypically like the second party?
e. is heterozygous for all genes?

Dont forget to explain me .....
i really appreciate.
Thanks
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Postby hemu0912 » Wed Jul 15, 2009 3:06 pm

no reply....yet :(
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Postby canalon » Wed Jul 15, 2009 8:43 pm

Draw your punnet squares, calculate outcomes. compare results using chi-square when necessary, and read the rules about homework questions.
Patrick

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any proof. (Ashley Montague)
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Postby hemu0912 » Thu Jul 16, 2009 12:54 am

thanks but it would be great if u explain me #3 n #9
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Postby canalon » Thu Jul 16, 2009 2:03 am

For #9 you just need to draw the punnet square. Then or each possible allele combination check what is the phenotype. Then count the number of possible allele assortment and the number allelle assortment that give you each phenotype, and that is the probability of each phenotype.

For #3 you have to make some hypotheses on the underlying genotype giving rise to the observed phenotype:
- type of transmission (i.e. recessive/dominant or codominance)
- gene linkage (i.e. are they on the same chromosome or not)
and calculate the distribution of phenotype in each case (just like above, draw punnet squares and count the sections)
Patrick

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Postby hemu0912 » Thu Jul 16, 2009 2:18 am

thanks buddy...
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