Question

Topic: Dihybrid cross
Usually tomato plants have purple stems, although in some varieties the purple pigment is missing and the stem is green. Most tomato plants have 'cut' leaves, but some have so-called 'potato' leaves.
Q: Calculate the genetic ratio for the following cross:
Purple stem, cut leaves X green stem, potato leaves

P.s No. of organisms for purple stem, cut leaves = 354
Purple stem, potato leaves= 0
green stem, cut leaves=367
green stem, potato leaves = 0

Really need help with this :/
Thanks in advance !

Answer 1

So you would have 2 different letters for this one because they are comparing 2 different traits. I assigned the letter 'a' to the color and 'L' to the leaf shape. You are going to have a dominate and recessive allele for each of the traits. So for the color the dominate one seems to be purple (because most are purple I'm just assuming) so that one would be represented by capital A. Green would be lowercase a (lowercase meaning recessive). Now for the shapes.. The dominate one seems to be the 'cut' leaf so i labeled that one as uppercase 'L'. The 'potato' one is going to be lowercase 'l'. Now the tough part comes to figuring out if they are heterozygous (meaning that they are both dominate and recessive, but if u have the dominant trait it will always be expressed as dominate). At first i tried the cross as AaLl (taking into consideration heterozygous) X aall (all recessive). I solved it using foil so your punnet squre will be AL Al aL al across the top and on the side al all the way down. I looked at the results and realized that there were no green potato plants so it couldnt be that. I then tried AaLLxaall, foil it out and you get AL AL aL aL across the top and then al all the way down, and it worked. The genetic ratio would be 50% AaLl and 50% aaLl. Sorry it was so long! I hoped this helped

Answer 2

Thank you sooo much! :D

Answer 3

No problem :)