Question

in peas, yellow seed color (y) is dominant to green seed color (y). a homozygous green seed pea plant is crossed with a heterozygous yellow seed pea plant. what is the predicted phenotypic ratio of the offspring based on seed color?
50 percent yellow, 50 percent green
50 percent yy, 50 percent yy
100 percent yellow, 0 percent green
100 percent yy, 0 percent yy

Explanation:

Step1: Determine Genotypes

Homozygous green: \( yy \) (since green is recessive, so it must be \( yy \)). Heterozygous yellow: \( Yy \) (yellow is dominant, heterozygous means one \( Y \) and one \( y \)).

Step2: Set Up Punnett Square

The cross is \( yy \times Yy \). The possible gametes from \( yy \) are all \( y \), and from \( Yy \) are \( Y \) and \( y \).

	\( Y \)	\( y \)
\( y \)	\( Yy \)	\( yy \)

Step3: Analyze Phenotypes

• \( Yy \) has yellow phenotype (dominant allele \( Y \) present).
• \( yy \) has green phenotype (recessive alleles only).

From the Punnett square, there are 2 \( Yy \) (yellow) and 2 \( yy \) (green) out of 4 offspring. So the phenotypic ratio is 50% yellow (\( Yy \)) and 50% green (\( yy \)).

Now, check the options:

• Option 1: 50 percent yellow, 50 percent green → matches our result.
• Option 2: 50 percent YY, 50 percent yy → Genotypic ratio (YY not possible here), incorrect.
• Option 3: 100 percent yellow, 0 percent green → Incorrect, we have green offspring.
• Option 4: 100 percent Yy, 0 percent yy → Incorrect, we have yy offspring.

Answer:

A. 50 percent yellow, 50 percent green