Dihybrid Cross Phenotypic Ratios

The video tutorial by Kevin Toke covers a detailed example of a dihybrid cross, focusing on genes A and B, which code for height and speed, respectively. Both maternal and paternal genotypes are heterozygous for these genes. The tutorial explains setting up a dihybrid cross, filling in the grid, and calculating genotypic and phenotypic ratios. It emphasizes the importance of correctly setting up the cross to ensure accurate results. The video concludes with a tip on memorizing the phenotypic ratio for heterozygous crosses.

What do genes A and B code for in the dihybrid cross example?

• A codes for weight, B for color

• A codes for speed, B for height

• A codes for height, B for speed

• A codes for color, B for size

How many cells are there in a dihybrid cross compared to a monohybrid cross?

• 4 cells in both

• 16 cells in dihybrid, 4 in monohybrid

• 4 cells in dihybrid, 16 in monohybrid

• 16 cells in both

What is the first step in setting up a dihybrid cross?

• Calculating the genotypic ratio

• Figuring out what goes in each column and row

• Determining the phenotypic ratio

• Filling in the cells randomly

What should the sum of all genotypic frequencies in a dihybrid cross add up to?

• 8

• 12

• 20

• 16

Why is the phenotypic ratio more commonly asked about than the genotypic ratio in dihybrid crosses?

• It is not more commonly asked

• It is less messy and more straightforward

• It provides more detailed information

• It is easier to calculate

What phenotype does a genotype of big A big A and little B little B result in?

• Tall and fast

• Short and slow

• Tall and slow

• Short and fast

What is the phenotype of an individual with the genotype little a little a and Big B Big B?

• Tall and slow

• Short and fast

• Short and slow

• Tall and fast

What is the phenotypic ratio for a dihybrid cross involving two heterozygous parents?

• 9:3:3:1

• 3:1

• 1:2:1

• 1:1

If both parents are heterozygous for two genes, what is the expected phenotypic ratio?

• 2:2:2:2

• 1:1:1:1

• 9:3:3:1

• 3:3:1:1

What is a key takeaway regarding the phenotypic ratio in dihybrid crosses with heterozygous parents?

• It is always 3:1

• It is always 1:1

• It is always 9:3:3:1

• It varies greatly