Genetics | Dihybrid Cross (Example 2)

The video tutorial explains the process of performing 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 covers setting up the dihybrid cross, filling in the 16 cells, and calculating both genotypic and phenotypic ratios. It emphasizes the importance of correctly setting up the cross and provides a shortcut for memorizing the phenotypic ratio of 9:3:3:1 when crossing two heterozygotes.

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

• A is for weight, B is for height

• A is for speed, B is for color

• A is for height, B is for speed

• A is for color, B is for texture

How many cells are there in a dihybrid cross grid?

• 12

• 16

• 8

• 4

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

• Determining the phenotypic ratio

• Arranging alleles in columns and rows

• Calculating the genotypic ratio

• Filling in the cells

What is the genotypic ratio for a dihybrid cross with heterozygous parents?

• 16:0

• 3:1

• 9:3:3:1

• 1:1:1:1

Which phenotype corresponds to the genotype 'big A, big A, little b, little b'?

• Tall and slow

• Short and fast

• Short and slow

• Tall and fast

How many individuals are tall and fast in the phenotypic ratio?

• 3

• 6

• 12

• 9

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

• 16:0

• 3:1

• 1:1:1:1

• 9:3:3:1

What is the phenotype for the genotype 'little a, little a, big B, big B'?

• Short and slow

• Tall and slow

• Short and fast

• Tall and fast

What is the phenotype for the genotype 'little a, little a, little b, little b'?

• Tall and fast

• Short and fast

• Tall and slow

• Short and slow

What is the key takeaway for memorizing phenotypic ratios in dihybrid crosses?

• Use a calculator

• Memorize the 9:3:3:1 ratio for heterozygous parents

• Always calculate manually

• Ignore phenotypic ratios