Question

multiple choice 1 point
10
in peas the trait for tall plants is dominant (t) and the trait for short plants is recessive (t). the trait for yellow seed color is dominant (y) and the trait for green seed color is recessive (y). a cross between two plants results in 296 tall yellow plants and 104 tall green plants. which of the following are most likely to be the genotypes of the parents?
ttyy × ttyy
ttyy × ttyy
ttyy × ttyy
ttyy × ttyy
ttyy × ttyy

Explanation:

Step1: Analyze plant height trait

All offspring are tall (296 + 104 = 400 tall, 0 short). So at least one parent must be homozygous dominant (TT) for height, or both have at least one T. But since all are tall, likely one or both TT.

Step2: Analyze seed color trait

Yellow (Y) is dominant, green (y) recessive. Offspring: 296 yellow, 104 green. Ratio ≈ 3:1 (296/104 ≈ 2.84 ≈ 3). This is a typical monohybrid cross ratio for heterozygous parents (Yy × Yy), as Yy × Yy gives 3/4 Y_ (yellow), 1/4 yy (green).

Step3: Evaluate parent genotypes

For height: All tall offspring, so at least one parent TT (or both). For color: 3:1 ratio, so parents must be Yy × Yy. Now check options:

• Option 1: TTYy × TTYy. Height: TT × TT → all TT (tall). Color: Yy × Yy → 3:1 yellow:green. Matches offspring.
• Other options: e.g., TtYy × TtYy would have short plants (tt) if both Tt, but no short offspring. So TTYy × TTYy is correct.

Answer:

The correct parent genotypes are TTYy × TTYy (assuming the first option is TTYy × TTYy, based on the ratio and trait analysis).