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

DIHYBRID CROSSES (Involves 2 Traits)

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?

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

Section 11-3 Figure Independent Assortment in Peas

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

LAW OF ______________________ the factors are distributed to gametes independently of other factors Mendel’s second law of genetics INDEPENDENT ASSORTMENT Image modified from:

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

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

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

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

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

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

POSSIBLE PARENT GAMETES? RYRY ryry RyRy rYrY

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 RRYY RRYy RrYYRrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy heterozygous dihybrid

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

PRACTICE MAKING GAMETES FOR DIHYBRID CROSSES

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

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

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

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

DIHYBRID CROSS Dihybrid Cross