1. INTRODUCTION TO GENETICS CHAPTER 6: MEIOSIS AND MENDEL DIHYBRIDS AND TEST CROSSES

2. DIHYBRID CROSSES (Involves 2 Traits)

3. Another question Mendel proposed? Does the gene that determines if a seed is round or wrinkled have anything to do with the gene for seed shape? Must a seed that is yellow also be round?

4. MAKING A CROSS WITH ___________________= ____________________ A Punnett square for a DIHYBRID CROSS looks like this: DIHYBRID CROSS TWO gene traits

5. Section 11-3 Figure 11-10 Independent Assortment in Peas

6. REVIEW: LAW OF SEGREGATION (MENDEL’S FIRST LAW OF GENETICS Organisms inherit two copies of each gene, one from each parent Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate, or separate, during gamete formation

7. LAW OF ______________________ the factors are distributed to gametes independently of other factors Mendel’s second law of genetics INDEPENDENT ASSORTMENT Image modified from: http://anthro.palomar.edu/mendel/mendel_1.htm

8. 1. ___________ what _________________ are 2. ________correct__________ square __________ 3. ______ possible_______________________ 4. ______ boxes with _____________________ 5. Determine ____________of_____________& ____________ LET’S MAKE A DIHYBRID CROSS R – YELLOWY - ROUND r – greeny - wrinkled HOMOZYGOUS YELLOW ROUND rryy HOMOZYGOUS GREEN WRINKLED Figure out parent alleles Choose Punnett size Put in parent gametes Fill in offspring combinations probabilities phenotypes genotypes RRYY

9. R R Y YR R Y Y HOMOZYGOUS ROUND YELLOW PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE ? R-yellow, r-greenY-round, y-wrinkled Each gamete should get one of each kind of gene ___________ ____________ _____________ _____________ R YR Y R YR YR YR Y R YR Y

10. r r y yr r y y HOMOZYGOUS WRINKLED GREEN PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE ? R-yellow, r-greenY-round, y-wrinkled Each gamete should get one of each kind of gene ___________ ____________ _____________ _____________ r y r yr y r yr y r yr y

11. RY 100% of offspring = _______ genotype _______________________ phenotype RrYy ROUND YELLOW RrYy RrYy RrYyRrYy RrYy RrYy

12. R r Y yR r Y y R r Y yR r Y y HETEROZYGOUS ROUND YELLOW MAKE ANOTHER CROSS R-yellow, r-greenY-round, y-wrinkled X

13. R r Y yR r Y y HETEROZYGOUS ROUND YELLOW PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE ? R-yellow, r-greenY-round, y-wrinkled Each gamete should get one of each kind of gene ___________ ____________ _____________ _____________ R YR Y r yr y r Yr YR yR y

14. POSSIBLE PARENT GAMETES? RYRY ryry RyRy rYrY

15. RY RyrYry RY Ry rY ry Sign of a ______________________ cross is a _____________ ratio in offspring. 9:3:3:1 ____ Round & Yellow ____ Round & green ____ Wrinkled & yellow ____ wrinkled & green 9 3 3 1 RRYY RRYy RrYYRrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy heterozygous dihybrid

16. __________ratio is a clue that it’s a ____________________________cross ____ ____________ TRAIT 1 ; ____________ TRAIT 2 ____ ____________ TRAIT 1; _____________ TRAIT 2 9 3 3 1 9:3:3:1 HETEROZYGOUS TWO gene dominant dominant recessive recessive dominant recessive

17. PRACTICE MAKING GAMETES FOR DIHYBRID CROSSES http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html

18. pure round & pure tall = __________ ____ ____ ___________ What gametes can it produce? WHAT ARE THE POSSIBLE GAMETES? Round-R, Wrinkled-rTall-T, Short-t   R R T T R T   R TR TR TR T

19. Heterozygous Tall = __________ & pure round ____ ____ ___________ What gametes can it produce? WHAT ARE THE POSSIBLE GAMETES? Round-R, Wrinkled-rTall-T, Short-t   RRTt RTRt   RT

20. Hybrid tall = __________ & pure wrinkled ____ ____ ___________ What gametes can it produce? WHAT ARE THE POSSIBLE GAMETES? Round-R, Wrinkled-rTall-T, Short-t   rrTt rTrt   rTrt

21. Heterozygous tall = __________ & hybrid round ____ ____ ___________ What gametes can it produce? WHAT ARE THE POSSIBLE GAMETES? Round-R, Wrinkled-rTall-T, Short-t   RrTt RTrT   rtRt

22. DIHYBRID CROSS Dihybrid Cross