independent assortment?

Stephen Modena nmodena at unity.ncsu.edu
Mon Feb 3 07:19:29 EST 1992


In article <92033.201318U50701 at uicvm.uic.edu> U50701 at uicvm.uic.edu (Yakof) writes:
>Hello there. I am taking introductory genetics this semester and one of the hom
>eworks asks to explain how 15:1 phenotypic ratio can be obtained from selfing
> F2; it is also specified that P1 were both pure lines. They are talking of mon
>ohybrid cross, by the way,  but I do not see any possible way of getting 15:1 p
>henotypic ratio.
>Is anybody there willing to help out?
>Thanks a lot.

Yakof,

Moma is  AABB

Popa is aabb

IF Baby is A_B_, (15/16 cases) then baby looks like Moma.
IF Baby is aabb, (1/16 cases) the Baby looks like Dada.
This is an examlpe of dominant epistatasis, I believe.

Elementary, my Dear Watson!

BUT! Suppose:

Moma is AAbb

Popa is aaBB

IF Baby is A_B_, (15/16 cases) then Baby looks like the Milkman
IF Baby is aabb, then Baby looks like Mom and Dad.

By Jove, Holmes! Coupling and repulsion!

Isn't genetics fun, when you say it this way?.

The real problem is that you are writing genotypes on paper, instead of
picking actual genetic cases.  Get Schaums Outline of Genetics and work
with real phenotypes and picture them in your mind as you do Punnet
Squares.

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