Question

there are genes that govern the eye color of mice, too. suppose that a true - breeding mouse with red eyes is crossed with a true - breeding mouse with black eyes. all of the offspring mice have black eyes. what can you conclude? the allele for red eyes is dominant. the allele for black eyes is dominant. neither. you need more data.

Explanation:

When true - breeding organisms with different traits are crossed and all offspring show one trait, that trait's allele is dominant. Here, red - eyed and black - eyed true - breeding mice are crossed and all offspring have black eyes, so the black - eye allele is dominant.

Answer:

The allele for black eyes is dominant