Use Punnett square to determine all of offspring genotypes & their relative frequencies from following cross..

Question

Use the Punnett square to determine all of the offspring genotypes and their relative frequencies from the following crosses.


a. Rr x Rr

b. Rr x rr

c. RR x Rr

I don't understand what "relative frequencies" mean. How do I get that? I understand that I have to make Punnett squares for each one, but what is the second part of the question asking really?

Answer 1

The way this is worded, "offspring genotypes and their relative frequencies," means that you are supposed to find the genotype ratio from the crosses.

Usually we find frequencies of the individual alleles, but that's not what the question is asking.

a. Rr x Rr
Punnett square will have in the boxes: RR, Rr, rR, rr
Those are the offspring genotypes.
The relative frequencies of the genotypes is 1RR: 2Rr: 1rr.
If your teacher wants these in percents or decimals, it's easily changed to 25% RR: 50% Rr: 25% rr or to 0.25 RR: 0.50 Rr: 0.25 rr.

b. Rr x rr produces Rr, Rr, rr, rr in the Punnett square.
1 Rr: 1 rr (It's 2 Rr: 2 rr but you reduce a ratio just like a fraction.)

c. RR x Rr produces RR, Rr, RR, Rr
1 RR: 1Rr

Answer 2

Basically, it means to find the genotypic ratios.

So, as an example, for a, you'd make a Punnet square. You'd find that the "rr" genotype would occur 1/4 of the time (fills 1 out of 4 squares.) That's all they're looking for.

So in the case of a, the answer would be 1:2:1. (1 RR: 2 Rr:1rr)

Answer 3

OK, when you do the punnet square for Rr x Rr, you get RR, Rr, Rr, rr. The relative frequencies for that one are

Genotype Rel Freq
RR 1
Rr 2
rr 1

You do that for all of them and add them up, I assume.

Answer 4

Umm I found this about relative frequency, it means "In biology, relative frequency is the occurrence of a single gene in a specific species that makes up a gene pool."

I've never had to do that in Bio!!