1. Dihybrid Punnett Squares
This tests for two traits!
Lets cross RRYY with rryy
List the phenotypes of the offspring RY RY RY RY
RrYy ry ry ry ry

2. Dihybrid Cross RY Ry rY ry RY Ry rY ry
Try crossing two heterozygous parents: RrYy & RrYy
List the genotypes, phenotypes & probability of the offspring: RY Ry rY ry
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy RY Ry rY ry

3. Incomplete Dominance
If you cross a red four o’clock flower with a white four o’clock flower which one will be the dominant color?
Neither! The flowers will be pink!
When neither allele is completely dominant over another this is called incomplete dominance

4. Incomplete Dominance Cross
Red four o’clocks are RR
White four o’clocks are R’R’
All offspring are pink!! R R R’ R’

5. The second (F2) generation!
Now cross two pink offspring!
What do the offspring look like?
(1 red, 1 white, 2 pink) R R’ R R’

6. Co-dominance
This is when both alleles express themselves in the offspring equally
Red horse (R ) crosses with a white horse (W)
All offspring will be roan (every other hair is white) R R W W