Genes are segments of DNA that contain “instructions” for the expression of traits. The presence of just one dominant gene in a chromosome pair results in expression of a certain trait. A recessive gene, on the other hand, will only result in the expression of a trait if the gene appears in both paired chromosomes.
In guinea pigs, the gene for black coat color is the dominant gene, and the gene for white coat color is the recessive gene.
A guinea pig has a black coat. Which of these explanations could be POSSIBLE?
a. The guinea pig received a recessive gene for white coat color from one
parent and no gene for coat color from the other parent.
b. The guinea pig received a dominant gene for black coat color from one
parent and no gene for coat color from the other parent.
c. The guinea pig received a dominant gene for black coat color from one
parent and a recessive gene for white coat color from the other parent.
d. The guinea pig received a recessive gene for white coat color from one
parent and a recessive gene for white coat color from the other parent.
C. However, if the gene is sex-linked (on the X chromosome), a male offspring could get B.
c. The guinea pig received a dominant gene for black coat color from one parent and a recessive gene for white coat color from the other parent.
To determine the possible explanation for a guinea pig having a black coat, we need to consider the nature of dominant and recessive genes. As mentioned, the gene for black coat color is dominant, while the gene for white coat color is recessive.
If a guinea pig has a black coat, it means that the black coat gene is expressed. This can occur in two ways: either the guinea pig received a dominant gene for black coat color from one parent or the guinea pig received a dominant gene for black coat color from both parents.
Now let's go through each option to see which ones are possible:
a. The guinea pig received a recessive gene for white coat color from one parent and no gene for coat color from the other parent.
- This option is NOT possible because the guinea pig has a black coat, which means it must have a dominant gene for black coat color.
b. The guinea pig received a dominant gene for black coat color from one parent and no gene for coat color from the other parent.
- This option is NOT possible because the guinea pig has a black coat, which means it must have a dominant gene for black coat color.
c. The guinea pig received a dominant gene for black coat color from one parent and a recessive gene for white coat color from the other parent.
- This option is POSSIBLE. If the guinea pig received a dominant gene for black coat color from one parent and a recessive gene for white coat color from the other parent, the dominant black coat gene would be expressed.
d. The guinea pig received a recessive gene for white coat color from one parent and a recessive gene for white coat color from the other parent.
- This option is NOT possible because the guinea pig has a black coat, which means it must have at least one dominant gene for black coat color.
Based on this analysis, the possible explanation for the guinea pig having a black coat is c. The guinea pig received a dominant gene for black coat color from one parent and a recessive gene for white coat color from the other parent.