Dihybrid cross?

Question

I already understand what a dihybrid is etc., but how is it formed? Or is it just a fiction? I know it's always two traits. I understand how a genotype is formed (Aa) - two alleles from two chromosomes, but how is AaGg formed? Thank you.

Answer 1

Hey hun. I had myself once asking myself this question. Well, I looked into it more. Here is a site that will help you in so many ways.

http://www.treca.org/staff/voss/Pages/dihybrid.html

I hope I could help you out, good luck! <3

Answer 2

See the wiki page

Big punnett square

AAGG x aagg

-> AaGg
is the simplest

In the pea plant, two characteristics for the peas, shape and color, will be used to demonstrate an example of a dihybrid cross in a punnett square. R is the dominant gene for roundness for shape, with lower-case r to stand for the recessive wrinkled shape. Y stands for the dominant yellow pea, and lower-case y stands for the recessive green color. By using a punnett square (the gametes are RY, Ry, rY, and ry):
____RY_____Ry____rY____ry
RY_RRYY__RRYy__RrYY__RrYy
Ry_RRYy___RRyy__RrYy__Rryy
rY__RrYY___RrYy___rrYY__rrYy
ry__RrYy___Rryy___rrYy___rryy


The result in this cross is a 9:3:3:1 phenotypic ratio, as shown by the colors, where yellow represents a round yellow (both dominant genes) phenotype, green representing a round green phenotype, red representing a wrinkled yellow phenotype, and blue representing a wrinkled green phenotype (both recessive genes).

Answer 3

There are a couple of ways to get this kind of genotype. Let's use specific examples so you can see...Tongue rolling is dominant over non-rolling (R and r) and brown eyes (B) are dominant to blue (b).

So, if you cross a blue-eyed, homozygous roller (RRbb) with a homozygous brown-eyed, non-roller (rrBB), all of their offspring will be dihybrids (RrBb).

Or, you could take a homozygous brown-eyed, homozygous roller (RRBB) and cross it with a blue-eyed, non-roller (rrbb). Again, all offspring will be brown-eyed rollers (RrBb).