Genetics And Evolution Principles Of Inheritance And Variation 3-P-5

Question: In the F₁ generation of a dihybrid cross, what is the probability of obtaining individuals that are homozygous for both traits?#

A) 1/2

B) 3/4

C) 1/3

D) 1/4

Answer: D) 1/4#

Explanation: In a dihybrid cross, we are typically dealing with two traits, each with two alleles. Let’s denote the alleles for the first trait as A (dominant) and a (recessive), and for the second trait as B (dominant) and b (recessive).

When we perform a dihybrid cross between two heterozygous individuals (AaBb x AaBb), the F1 generation will have a variety of genotypes. To find the probability of obtaining individuals that are homozygous for both traits, we need to consider the combinations that result in homozygosity for both traits (AABB, AAbb, aaBB, aabb).

The probability of being homozygous for the first trait (AA or aa) is 1/4 for each:

• AA: 1/4
• aa: 1/4

The probability of being homozygous for the second trait (BB or bb) is also 1/4 for each:

• BB: 1/4
• bb: 1/4

To find the probability of being homozygous for both traits, we multiply the probabilities for each trait:

• AABB: (1/4) * (1/4) = 1/16
• AAbb: (1/4) * (1/4) = 1/16
• aaBB: (1/4) * (1/4) = 1/16
• aabb: (1/4) * (1/4) = 1/16

Adding these probabilities together gives us the total probability of being homozygous for both traits: 1/16 + 1/16 + 1/16 + 1/16 = 4/16 = 1/4

Therefore, the probability of obtaining individuals that are homozygous for both traits in the F1 generation of a dihybrid cross is: D) 1/4