1. Two trait genetic crosses & pedigrees

2. P = PpSs x ppss Crossing Two Traits
Cross a heterozygous purple, heterozygous smooth corn plant with a corn plant that is yellow and wrinkled.
Purple = P
Yellow = p
Smooth = S
Wrinkled = s
P = PpSs x ppss 2

3. P = PpSs x ppss x ps PS Ps pS ps
Step #1 Determine genotypes of parents.
Step #2 Determine the gametes of each parent.
Step #3
Set up Punnett Squares ps PS Ps pS ps x 3

4. PpSs ppss PpSs Ppss ppSs ppss ps PS Ps pS ps 25% Purple & Smooth
25% Purple & Wrinkled pS
ppSs
25% Yellow & Smooth
ppss ps
25% Yellow & Wrinkled 4

5. P = TtAa x TtAa What is a dihybrid cross? ta TA Ta tA TA TTAa TtAA5

6. Dihybrid Cross Ratio 9/16 Tall & Axial (Dom & Dom)
3/16 Tall & Terminal (Dom & Rec)
3/16 Short & Axial (Rec & Dom)
1/16 Short & Terminal (Rec & Rec) 6

7. Pedigrees
A pedigree is a type of family tree that shows the sex of the individuals and the phenotype of that individual for a single trait
Circles are female ,squares are male
Filled in has the ‘affected’ phenotype, open has the ‘unaffected’
The trait examined can either be dominant or recessive
A person who has the trait but does not express it is a “carrier”
(heterozygous for a recessive trait)

8. Using Pedigrees
A pedigree can be used to determine the genotype of individuals in a family
It can be used to track a, dominant, recessive , or sex-linked trait
Pair share: is the trait dominant or receive? How do you know? If it is recessive are there any carriers?

9. What does this pedigree tell us?

10. White board Review
What are the 3 steps of determining a dihybrid cross?
What does “di” mean?
What is a pedigree?