Dihybrid Crosses

1
Dihybrid Crosses

• Chapter 9
• Section 9-2

2
General Question

• What happens when I cross a plant that has
  yellow, round seeds with a plant that has green
  wrinkled seeds?

3
Monohybrid Cross Review
4
Dihybrid Cross

• A cross between individuals that involves two
  pairs of contrasting traits.
• Example pea plants where seeds are green or
  yellow in color and are smooth or wrinkled in
  appearance.
• R round dominant seed shape
• r wrinkled recessive seed shape
• Y yellow dominant seed color
• y green recessive seed color

5
Homozygous x Homozygous
RRYY
R,r shape Y,y color
rryy
6
Heterozygous x Heterozygous
RrYy
R,r shape Y,y color
RrYy
7
Dihybrid Cross for Martians
A green a yellow G tall g short
8
Dihybrid Cross
A green a yellow G tall g short
9
Genotypes?
AaGG AaGg Aagg aaGG aaGg aagg
2
4
2
2
4
2
10
Phenotypes?
A green a yellow G tall g short
Green Tall Green Short Yellow Tall
Yellow Short
6
2
6
2
11
The Breakdown

• A cross between individuals involving two pairs
  of contrasting traits is called a _____________.

dihybrid cross
12
Section Review

• Answer question 5 on page 178.
• Answer questions 13 and 18 on page 180 and
  Critical Thinking 2 and 3 on page 181.

13
Next Class

• More Dihybrid exercises!
• Test Next Thursday
• (February 1) for Chapter 9!