DIHYBRID PUNNETT SQUARES https www youtube comwatch vq

DIHYBRID PUNNETT SQUARES https: //www. youtube. com/watch? v=q. IGXTJ Lr. Lf 8

Dihybrid Cross: a cross that shows the possible offspring for two traits Trait Two Trait one Fur Color: Color B: Black b: White Coat Texture: Texture R: Rough r: Smooth Step 1: FIND OUT THE GENOTYPES OF THE PARENTS In this example, we will cross a heterozygous individual with another heterozygous individual. Their genotypes will be: Bb. Rr x Bb. Rr

Dihybrid Cross Bb. Rr x Bb. Rr DAD MOM Step 2: FOIL EACH PARENT TO SHOW THE POSSIBLE GAMETE COMBINATIONS Remember, each gamete must have one B and one R.

F. O. I. L. PARENT 1 Bb. Rr BR Br b. R br PARENT 2 Bb. Rr BR Br b. R br

Practice What are the possible gametes for BBrr What are the possible gametes for Hh. TT?

Dihybrid Cross Bb. Rr x Bb. Rr DAD MOM Step 3: SET UP PUNNETT SQUARE: Arrange all possible gametes for dad on the top of your Punnett Square, and mom down the side

Dihybrid Crosses: a cross that shows the possible offspring for two traits Bb. Rr x Bb. Rr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth Step 4: Fill in the Punnett Square (find the possible genotypes of the offspring) BR Br BR BB R R BB r R br b. B RR b. B r R Br B B R r BB r r b. B R r b. B r r b. R Bb RR Bb r R bb R R b b r. R br Bb R r Bb r r bb R r bb r r

How many of the offspring would have a black, rough coat? How many of the offspring would have a black, smooth coat? How many of the offspring would have a white, rough coat? How many of the offspring would have a white, smooth coat? BR Br b. R br BR BBRr Bb. RR Bb. Rr Br BBRr BBrr Bb. Rr Bbrr b. R Bb. Rr bb. RR bb. Rr br Bb. Rr Bbrr bb. Rr bbrr Fur Color: Coat Texture: B: Black R: Rough b: White r: Smooth

How many of the offspring would have black, rough coat? How many of the offspring would have a black, smooth coat? How many of the offspring would have a white, rough coat? BR Br b. R br BR BBRr Bb. RR Bb. Rr Br BBRr BBrr Bb. Rr Bbrr b. R Bb. Rr bb. RR bb. Rr br Bb. Rr Bbrr bb. Rr bbrr How many of the offspring would have a white, smooth coat? Phenotypic Ratio= 9: 3: 3: 1 Fur Color: Coat Texture: B: Black R: Rough b: White r: Smooth

Practice in your notes… In pea plants, yellow seeds (Y) are dominant over green seeds (y), and rounded peas (R) are dominant over wrinkled peas (r). Cross a plant that is heterozygous for both traits with a plant that is homozygous recessive for both traits. Draw a Punnett square to show all possible offspring, and determine the genotypic and phenotypic ratios.

Yy. Rr X yyrr YR Yr y. R yr yr Yy. Rr Yyrr yy. Rr yyrr

More Practice • Work on the Sponge. Bob Dihybrid Cross worksheet. Turn it in at the end of class.