Anonymous

We are working on dihybrid crosses in biology class, and I am just not getting it. Here is what the problem says: In a certain set of lab mice, black hair is dominant to white hair, and coarse hair is dominant to fine hair. Determine the percentage of black, fine-haired offspring that will result if two mice heterozygous for both of these traits are mated. Draw a Punnet Square to support your answer.

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When I did this, I got 2/16 or1/8....is that right?

Relevance

shure! so a dyhbrid cross is when you combine two characteristics into a P-square. with 2 different types of each characteristic, that gives you 4 different different gene combos.

lets say B=black hair, and b=white, C=coarse, c=fine so the combos are

BC Bc bC bc right?

so cross that with another BC Bc bC bc

the dominant traits will overcome the recessive so BbCc will look BC...You are looking for black (B) fine haired (c) so BBcc or Bbcc

BC...........Bc........bC bc

BC.....BBCC.....BBCc...BbCC....BbCc

Bc......BBCc......BBcc....BbCc....Bbcc

bC......BbCC.....BbCc....bbCC....bbCc

bc.......BbCc.....Bbcc......bbCc....bbcc

there ya go! get to counting!

Yahoo hates my charts, and makes like a bunch of spaces olny one space, so it was hard to draw that and it might not come out right...