# AP BIOLOGY

## HEREDITY

### MONOHYBRID CROSS

 Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
What is the correct prediction when crossing a homozygous dominant parent with a homozygous recessive parent in dihybrid cross?
 A 75% dominant, 25% recessive B 1:2:1 C 9:3:3:1 D 100% heterozygous
Explanation:

Detailed explanation-1: -For example, if one parent is homozygous dominant (WW) and the other is homozygous recessive (ww), then all their offspring will be heterozygous (Ww) and possess a widow’s peak.

Detailed explanation-2: -In a test cross, the dominant-expressing organism is crossed with an organism that is homozygous recessive for the same characteristic. If the dominant-expressing organism is a homozygote, then all F1 offspring will be heterozygotes expressing the dominant trait (Figure 8.8).

Detailed explanation-3: -If a homozygous dominant is crossed with a heterozygote, the probability that an offspring will be homozygous recessive is 0%. 10. 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-4: -In a mendelian dihybrid cross, the ratio among homozygous dominant (RRYY), pure heterozygous (RrYy) and homozygous recessive (rryy) traits in F2 generation in a pea plant is 1:4:1.

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