Please help me on how to do Science DNA punnett squares!

Question

How do you do DNA punnett squares? My science teacher showed me an activity we all have to do but he never really explained it so I'm confused. What I know so far is the fact that Dominant alleles take over Recessive alleles. Like Rr and RR is going to show dominant traits and only rr will show the recessive traits but I'm not sure. I also know that Homozygous is RR and rr while Heterozygous is Rr.

Answer 1

Example of a Punnett Square:

Aa x Aa

It's important to understand that the gametes produced by one parent go on the top, and the gametes of the other parent go along the left side.

Creating the square is the easy part. The part that most people get stuck on is computing the phenotypic and genotypic ratios.

Answer 2

What you have said above is absolutely correct. I feel that you have a better understanding of this than you might think...

So, a punnett square is a useful tool in looking at the heritability of a single trait or two traits; there is a more advanced method for looking at three or more traits. When you set up a punnet square with one trait, this is called a monohybrid cross (mono meaning a single trait).

Image: https://i.pinimg.com/originals/7b/97/c4/7b97c4915aed99c2e31b4b8d97a4e1d4.jpg

You will have to open in new tab by copy and pasting link.

This picture is probably similar to what your teacher showed you. So the letters of the top represent one parent and the letters to the left represent the other parent. The reason each parent has two letters is because they received two alleles (version of gene); one from each parent. The spaces with the flowers in them represent the offspring and each offspring also receives two alleles of the gene; one from each parent. In this case B (purple) is dominant to white, which means, in order for there to be a white flower, it must have two small b's (bb).

This can be very confusing at first, but once you start doing them, it makes much more sense. Please let me know if you have any other question. I'd be happy to help.