Dihybrid Cross Concepts and Ratios

The video tutorial explains the concept of a dihybrid cross, focusing on two traits: color and shape of pea plants. It describes the alleles involved, with capital letters representing dominant traits and small letters representing recessive traits. The tutorial demonstrates how to perform a dihybrid cross using the foil method to obtain haploid gametes and fill in a Punnett square. It also covers calculating phenotypic and genotypic ratios, highlighting the 9:3:3:1 ratio pattern. The video concludes with a discussion on how these patterns change with different gametes, while the method remains consistent.

What is a dihybrid cross?

• A cross considering one trait

• A cross considering three traits

• A cross considering four traits

• A cross considering two traits

Which allele represents the dominant color trait in pea plants?

• Y

• r

• R

• y

What does the presence of a capital letter in a genotype indicate?

• Recessive trait

• Dominant trait

• Neutral trait

• Incomplete dominance

Which method is used to obtain haploid gametes in a dihybrid cross?

• Split method

• Combine method

• Cross method

• Foil method

What is the first step in filling a Punnett square?

• Mix alleles randomly

• Write alleles in alphabetical order

• Write the dominant alleles first

• Write the recessive alleles first

What is the genotype of a pea plant with yellow and smooth traits?

• yyRr

• yyrr

• YYRR

• YyRr

How many yellow smooth phenotypes are there in a typical dihybrid cross?

• 12

• 9

• 6

• 3

What is the phenotypic ratio in a dihybrid cross?

• 4:4:4:4

• 9:3:3:1

• 3:1

• 1:2:1

What pattern is observed in the genotypic ratio of a dihybrid cross?

• Horizontal

• Vertical

• Circular

• Diagonal

What remains constant in the method of solving a dihybrid cross?

• The alleles

• The ratio

• The pattern

• The method