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Download Two trait crosses - Sonoma Valley High School
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Two trait genetic crosses & pedigrees 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 P = PpSs x ppss ps PS Ps pS ps x Step #1 Determine genotypes of parents. Step #2 Determine the gametes of each parent. Step #3 Set up Punnett Squares PpSs ps ppss PS PpSs 25% Purple & Smooth Ps Ppss 25% Purple & Wrinkled pS ppSs 25% Yellow & Smooth ps ppss 25% Yellow & Wrinkled What is a dihybrid cross? P = TtAa x TtAa tA ta TA Ta TA TTAA TTAa TtAA TtAa Ta TTAa TTaa TtAa Ttaa tA TtAA TtAa ttAA ttAa ta TtAa Ttaa ttAa ttaa 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) 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 1. What are the 3 steps of determining a dihybrid cross? 2. What does “di” mean? 3. What is a pedigree?
