I really need help with the Punnett square & genotypic

by **Paigebentley** » Thu Jan 24, 2013 4:34 am

Hi, I'm new to this and really need your help with this question. Genetics are not my strong point in bio. Please help me with this. Thanks

1. A backyard gardener had seeds from a variety of peas that were hybrids (heterozygous) for red flower colour. In peas, red flower colour (R) is dominant to white flower colour (r). If these plants were allowed to self-pollinate and produced 1284 seeds, use a Punnett square to predict the genotypic and phenotypic rations for the F1 and F2 generations.

by **JackBean** » Thu Jan 24, 2013 11:23 am

If they were all heterozygotes, they must be Rr. That should be easy. Now you have to do Punnett:

.... R .. r
R . RR . Rr
r . Rr . rr

thus you see that F1 will be genotypically RR : Rr : rr - 1 : 2 : 1. It should be easy to make phenotypic ratio from that.
F2 generation will be pretty hard, because one can combine all three of them for each parent.

by **Paigebentley** » Fri Jan 25, 2013 7:22 am

Thank you JackBean, for taking your time and trying to help me.

Would 25% be Red, 50% Pink and 25% White?? Or would it be 3/4 Red because red is the dominant and 1/4 White? Sorry im just trying to understand this. Im still not sure what to do for the F1 F2 generations.

by **JackBean** » Fri Jan 25, 2013 9:47 am

they say dominant, but not whether it's completely dominant, hm :roll:

I'd try 75% red and 25% white

by **mavis** » Mon Feb 04, 2013 5:52 am

if there are 25% be Red, 50% Pink and 25% White, it means the red is incomplete dominant. when heterozygous, it wont be appeared as dominant phenotype, it will appear as pink colour.

In ur question,[(heterozygous) for red flower] this mean it is not incomplete dominant.