AP BIOLOGY

HEREDITY

MONOHYBRID CROSS

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

In a cross of a heterozygous with a homozygous dominant organism, what percent of the offspring are expected to have a recessive phenotype?

A	0%
B	25%
C	50%
D	75%
E	100%

Explanation:

Detailed explanation-1: -A monohybrid cross is a cross between two individuals with different alleles at one genetic locus. If we cross two heterozygous individuals (Aa), then the percentage of offsprings with recessive phenotype will be: Aa x Aa = AA Aa Aa aa, so recessive phenotypes would be 1/4 = 25%. Thus, the correct answer is option D.

Detailed explanation-2: -If two heterozygotes are crossed, the probability that an offspring will be homozygous recessive is 25% or 0.25. Homozygous dominant: 25% or 0.25.

Detailed explanation-3: -The answer is 50%. Assume that the homozygous recessive trait is denoted by aa and the heterozygote is Aa.

Detailed explanation-4: -In any cross involving at least one parent that is homozygous dominant (2 CAPITAL letters), 100% of the offspring will have the dominant trait in their phenotype.

There is 1 question to complete.