The Law of independent assortment
Applies to a cross between 2 organisms hat are hybrid for
2 or more traits.
EX: pea plant sees can be yellow(Y) or green (y) and their
texture can be round (R) or wrinkled (r). To figure out the
possible outcomes you would use a dihybrid cross. When
this happens the phenotypic ration for the 16 possible
outcomes of the dihybrid cross is ALWAYS 9:3:3:1
A pea plant that is heterozygous for round, yellow seeds is self fertilized, what are the phenotypic ratios of the
resulting offspring?
Step 1: Determine the parental genotypes from the text above, the word "heteroyzous" is the most important
clue, and you would also need to understand that self fertilized means you just cross it with itself.
RrYy x RrYy
Step 2: Determine the gametes. This might feel a little like the FOIL method you learned in math class.
Combine the R's and Ys of each parent to represent sperm and egg. Do this for both parents
Gametes after "FOIL“
RY, Ry, rY, ry (parent 1) and RY, Ry, rY, ry (parent 2)
Gametes after "FOIL“
RY, Ry, rY, ry (parent 1) and RY, Ry, rY, ry (parent 2)
Step 3: Set up a large 4x4 Punnet square, place one
gamete set from the parent on the top, and the other on
the side
What are the parents of the dihybrid cross?
A.
B.
C.
D.
E.
F.
FF,EE
FF,ee
ff, EE
Ff, EE
Ff,Ee
FF, Ee
0%
0%
8%
0%
75%
17%
The genes being studied are f (fancy tail) and (e)
funny eye. How many of the offspring are normal
tails, with normal eyes?
A. 9
B. 3
C. 1
92%
0%
8%
The genes being studied are f (fancy tail) and (e)
funny eye. How many of the offspring are normal
tails, with normal eyes?
A. 9
B. 3
C. 1
EXPLANATION
33%
33%
33%
The genes being studied are f (fancy tail) and (e)
funny eye. How many of the offspring are normal
tails, with funny eyes?
A. 9
B. 3
C. 1
0%
100%
0%
The genes being studied are f (fancy tail) and (e)
funny eye. How many of the offspring are normal
tails, with funny eyes?
A. 9
B. 3
C. 1
EXPLANATION
33%
33%
33%
The genes being studied are f (fancy tail) and (e)
funny eye. How many of the offspring are fancy
tails, with normal eyes?
A. 9
B. 3
C. 1
0%
100%
0%
The genes being studied are f (fancy tail) and (e)
funny eye. How many of the offspring are normal
tails, with funny eyes?
A. 9
B. 3
C. 1
EXPLANATION
33%
33%
33%
The genes being studied are f (fancy tail) and (e)
funny eye. How many of the offspring are fancy
tails, with funny eyes?
A. 9
B. 3
C. 1
0%
0%
100%
The genes being studied are f (fancy tail) and (e)
funny eye. How many of the offspring are normal
tails, with funny eyes?
A. 9
B. 3
C. 1
EXPLANATION
33%
33%
33%
The genes being studied are f (fancy tail) and (e) funny eye. The genotypes of both parents are Ff, Ee
Normal Tails with Normal Eyes-9
Fancy Tails with Normal Eyes-3
Normal Tails with Funny Eyes-3
Fancy Tails with Funny Eyes-1