Dihybrid Crosses

[flin5845]

---

Members don't see this ad.

Ok so I understand the concept behind the dihybrid crosses, but I was hoping for some advice that will shave off ALOT of time for me because I can get the right answers, but I almost have to draw out the 16 squares.

If a question reads from the cross CcSs x CcSs what is the probability of having an offspring that is CcSs?

I just can not do these problems in my head. Any advice?

 

[wthareuserious]

Ok so I understand the concept behind the dihybrid crosses, but I was hoping for some advice that will shave off ALOT of time for me because I can get the right answers, but I almost have to draw out the 16 squares.

If a question reads from the cross CcSs x CcSs what is the probability of having an offspring that is CcSs?

I just can not do these problems in my head. Any advice?

Just multiple the alleles out separately

so Cc x Cc gives you a 1/2 chance of Cc

and Ss x Ss gives you a 1/2 chance of Ss

so .5 x .5 = .25

 

[HannibalLecter]

Ok so I understand the concept behind the dihybrid crosses, but I was hoping for some advice that will shave off ALOT of time for me because I can get the right answers, but I almost have to draw out the 16 squares.

If a question reads from the cross CcSs x CcSs what is the probability of having an offspring that is CcSs?

I just can not do these problems in my head. Any advice?

I divide them up into two separate alleles, it really breaks it down to the basics and you can basically apply it to linked alleles as well. But since they are unlinked lets gooooooo:

Probability of C and c in the offspring:
(Probability of getting C from first parent (P1: CcSs) is 1/2 and probability of getting c from second parent (P2: CcSs) is 1/2) - Now this probability is doubled because it could be switched and that you could get c from the P1 and C from P2.
(1/2)(1/2)(2) = 1/2

Probability of getting S from P1: 1/2
s from P2: 1/2
Multiply by 2 because of twice the occurence
(1/2)x(1/2)x(2) = 1/2

Multiply both of the events occuring at the same time:

1/2 x 1/2 = 1/4

When you start seeing it that way it makes it really easy. Let me know if you have any harder ones and we will work them out