BELL WORK: In pigeons, ash-red feathers (B) are dominant to blue feathers (b). A heterozygous pigeon is crossed with a homozygous recessive pigeon. What percent of the offspring will have ash-red feathers? You do not have to copy the question, but you must complete a Punnett square!

B b Bb bb b b Bb bb

HOMEWORK!! Tonight’s homework: answer questions on the worksheet as you watch the video (same video as the last homework).

CO: I will predict genetic outcomes using dihybrid crosses CO: I will predict genetic outcomes using dihybrid crosses. LO: I will write notes and practice dihybrid crosses.

A Dihybrid Cross shows the possible offspring for two traits Coat Texture: R: Rough r: Smooth Fur Color: B: Black b: White In this example, we will cross a heterozygous individual with another heterozygous individual. Their genotypes will be: BbRr x BbRr

Dihybrid Cross BbRr x BbRr Step 1: Find ALL possible gametes that can be made from each parent. Remember, each gamete must have one B and one R.

Dihybrid Cross BbRr x BbRr Possible gametes: BR Br bR br Step 2: Arrange all possible gametes for one parent on the top of your Punnett Square and the other parent on the side

Dihybrid Crosses: a cross that shows the possible offspring for two traits BbRr x BbRr BR bR br Br Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth Step 3: Fill in the Punnett Square (find the possible genotypes of the offspring)

Dihybrid Crosses: a cross that shows the possible offspring for two traits BBRR BbRR BbRr BBRr BBrr Bbrr bbRR bbRr bbrr BbRr x BbRr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth

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 br Br BBRR BbRR BbRr BBRr BBrr Bbrr bbRR bbRr bbrr Fur Color: B: Black b: White Coat Texture: R: Rough 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? How many of the offspring would have a white, smooth coat? BR bR br Br BBRR BbRR BbRr BBRr BBrr Bbrr bbRR bbRr bbrr Phenotypic Ratio= 9:3:3:1 Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth

Mendelian Genetics Review Walk around the room and answer the review questions with a partner or by yourself. You do NOT have to write the question, but you MUST write the question NUMBER!

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 (what do you have to draw?) 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.