I have some questions that i really need help with!!?

Question

here they are

1. A brown guinea pig is crossed with a white one. All of the offspring are brown. Why?

2.Two white guinea pigs are crossed. All of the offspring are white. Why?

3.Two brown guinea pigs are crossed. All but one of the offspring is brown. The one is white. Why?

Thanks a lot

Answer 1

I'm guessing the brown gene is dominant over the white gene. So

1. Brown guinea pig is BROWN BROWN genotype,  white one is heterozygous - BROWN white genotype. When crossed, half will be BROWN BROWN the other half will be BROWN white, brown dominant so all brown phenotype.

2. White guinea pigs must be homozygous for the recessive white gene, so all offspring must be white.

3. Both brown pigs must be heterozygous, so 3/4 should be brown and 1/4 should be white.

Punnet squares!