Two trait genetic crosses & pedigrees

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

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

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

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

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

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)

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?

What does this pedigree tell us?

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