genetics problem about gametes, phenotype, genotype

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omegamon
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genetics problem about gametes, phenotype, genotype

Post by omegamon » Sat Oct 25, 2008 3:49 am

Hi i have questions about the genetic topic:
1) List all the different gametes produced by the following individuals:
a)AaBb b)AABBCc c)aaBbCc d)AaBbccDd

2) In guinea pigs, black coat color (allele B) is dominant to white (allele b). The allele for a rough coat (R) is dominant to the allele for a smmoth coat (r). What are the expected genotypic and phenotypic result for each of the folowing crosses? What is the ratio?

a) BBRR x bbrr b)BBrr x bbRR c) Bbrr x bbRr d) BBRr x BbRr e) BbRr x BbRr

Can you show me how you do these 2 problem ?

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canalon
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Post by canalon » Mon Oct 27, 2008 2:06 am

You just draw "Punnet squares" for 2 genes.
A search on Punnet squares on this site will tell you everything you need if you do not already know hw to draw them.
Patrick

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any proof. (Ashley Montague)

danni1708
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Re: genetics problem about gametes, phenotype, genotype

Post by danni1708 » Thu Oct 30, 2008 1:02 am

in question 1..
i never understand those questions..
the following individuals
AaBb AABBCc and so on..
how do u work that out??
the guinea pig one is easy enough using punnet squares..
but i just always get confused with the above question

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canalon
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Post by canalon » Mon Nov 03, 2008 7:18 pm

They give you for each gene (A, B and C) the 2 alleles carried by each individual and ask you to think what gametes can be produced. Full grown individuals are diploid, but the gametes are haploid. So an AA individual will produce only A gametes, while Aa will produce A and a gametes.
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

Jineanelopez
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Post by Jineanelopez » Mon Dec 15, 2008 6:43 pm

Danni,
Its easier if you use a punt box. It will give you all the combinations possible. HTH!

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keenangp
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Re: genetics problem about gametes, phenotype, genotype

Post by keenangp » Mon Dec 15, 2008 10:02 pm

Hey there omega, I remember when our lab prof asked us to write up all possible gametes and we had no idea how to! It was crazy..

Ok so always remember what you're doing with the punnet square. You are separating alleles during gamete formation and gametes are haploid. Thus, each gamete only has one allele of a pair.

ex. BbCc

B and b are alleles of each other, and will be separated during gamete formation (meiosis).

C and c are alleles of each other, and will be separated during gamete formation.

So the possible combinations of gametes BC, Bc, bC, and bc.

Notice that no homologous alleles are repeated, because they must be separated. You will not find a Bb, or a Cc. I always find it easy to start from the beggining, So big B, then the first symbol of the next gene, Big C. Then big B to little c.. Then little b to big C, then little b to little c. Write it out and it'll seem super easy. Hope that helps! :D

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