Question

question 2 of 10
what should you expect to observe from a dihybrid cross of two individuals with different alleles for each characteristic?
a. an f₁ generation that shows only the dominant phenotype for each trait
b. an f₂ generation that shows only the dominant phenotype for each trait, but an f₁ generation that includes both phenotypes
c. an f₂ generation that shows only the dominant phenotype for each trait
d. f₁ and f₂ generations that show only the dominant phenotype for each trait

Explanation:

Step1: Dihybrid cross basics

When two individuals with different alleles for each characteristic (e.g., \( AABB\times aabb \)) are crossed in a dihybrid cross, in the \( F_1 \) generation, according to Mendel's law of dominance.

Step2: \( F_1 \) phenotype

The \( F_1 \) generation will have a genotype like \( AaBb \). Since \( A \) is dominant over \( a \) and \( B \) is dominant over \( b \), the \( F_1 \) shows only the dominant phenotype for each trait.

Step3: \( F_2 \) phenotype (not relevant for this option)

In the \( F_2 \) generation (formed by self - crossing \( F_1 \) individuals \( AaBb\times AaBb \)), there is a phenotypic ratio of \( 9:3:3:1 \) (showing both dominant and recessive phenotypes for different combinations of traits). But the question is about what to expect in terms of the general observation related to the options. Option A is correct as per \( F_1 \) generation characteristics from a standard dihybrid cross starting with pure - breeding parents (one with all dominant alleles and one with all recessive alleles for the two traits).

Answer:

A. An \( F_1 \) generation that shows only the dominant phenotype for each trait