Punnett Squares???

Question

We are studying them in class. If u have any info on it can u plz share. If u got smthn mean to say then dnt sai it.

Answer 1

I teach college genetics. Punnett squares are used to determine the probability of an offspring to have a particular genotype, if you are given the genotype of both parents. Punnet squares, however, are really only useful for single or two genes. A single gene punnett square has four probabilities, a two gene one has 16 probabilities. A three gene punnett square has 64 probabilities, so you can see where this would not be too useful to draw out!
To see this, draw a square with four boxes in it. Put the mother's genotype above, putting an B over one column, and a b over the other. Put the father's genotype on the left hand side of the square, putting a B beside one row, and a b beside the other row. Now fill in the four boxes. In the first row of boxes, you have the father's B allele. Put the B in each of the two boxes in the first row. In the 2nd row of boxes, put the b allele. Now go up to the mother's genotype. Above the first column of boxes, you have the mother's B allele. Put a B in each of the boxes in that column. above the 2nd column of boxes, you have a b allele. Put a b in each of those boxes. When you are done, you should have this:

BB Bb
Bb bb

These are your offspring's possible genotypes.


I can't draw punnet squares here, but I hope you get the idea. Mother and father are heterozygous (they have both an B allele and b allele). The offspring probabilities for a particular genotype therefore would be 1/4 (25%) BB, 2/4 (50%) Bb, and 1/4 (25%) bb.

I hope this helps!

Answer 2

i took bio last year. they are gene crossing tables. capital letters are expressed lower case or dorment. punnet squares start easy... 2x2 squares. Then your teacher will get tricky and give you 10x10 square which are annoying