Question

White (w) coat color in guinea pigs is recessive to black (W). In 1909, W. E. Castle and J. C. Phillips transplanted an ovary from a black guinea pig into a white female whose ovaries had been removed. They then mated this white female with a white male. All the offspring from the mating were black in color (W. E. Castle and J. C. Phillips, 1909, Science 30:312-313).

1.Which statement explains the results of this cross?
2.Select the genotype of the offspring from this cross.
3.Select the conclusions that are indicated by this experiment regarding the validity of the pangenesis and the germ‑plasm theories discussed.

Answer 1

The results of the cross between a white female guinea pig and a black male guinea pig can be explained by Mendelian genetics. The offspring from this cross would have the genotype Ww. This experiment supports the validity of the germ-plasm theory.

Step-by-step explanation:

The results of the cross between a white female guinea pig and a black male guinea pig can be explained by the principles of Mendelian genetics. In guinea pigs, the white coat color is recessive to the black coat color. So when the white female's ovaries were removed and replaced with the ovaries of a black female, the resulting mating with a white male would produce offspring with the dominant black coat color.

The genotype of the offspring from this cross would be Ww, where W represents the black allele and w represents the white allele. Since the white female had two copies of the recessive white allele (ww) and the black male had two copies of the dominant black allele (WW), all the offspring would inherit one copy of the black allele from the male and one copy of the white allele from the female, resulting in the Ww genotype.

This experiment supports the validity of the germ-plasm theory, which states that hereditary information is carried in germ cells (sperm and eggs) and is not influenced by somatic cells. By transplanting the ovaries of a black guinea pig into a white female, the researchers ensured that the only genetic information passed on to the offspring was from the black guinea pig, regardless of the coat color of the recipient female.