In a population of weasels, black (B) and white (W) are co-dominant traits. The heterozygous genotype produces black and white spotted weasels. Consider the genetic cross shown in Punnett square. If there are 40 baby weasels born as a result of the cross, how many should be black?

Question

Responses
A 0
B 5
C 10
D 20

Answer 1

In a cross involving co-dominant traits, let's denote the black trait as "B" and the white trait as "W". The phenotypes for the genotypes would be:

• BB: Black weasel
• WW: White weasel
• BW: Black and white spotted weasel

Assuming the cross is between two heterozygous parents (BW x BW), the Punnett square would look like this:

      B     W
    -----------
B |   BB   |  BW  |
    -----------
W |   BW   |  WW  |

From the Punnett square, the genotypic ratio is:

• 1 BB (black)
• 2 BW (black and white spotted)
• 1 WW (white)

This means the phenotypic ratio is:

• 1 Black (BB)
• 2 Spotted (BW)
• 1 White (WW)

In total, there are 4 offspring (1 BB + 2 BW + 1 WW).

If there are 40 baby weasels, we can divide the total number by the phenotypic ratio.

The number of black weasels (BB) would be:

\[ \text{Number of Black Weasels} = \frac{1}{4} \times 40 = 10 \]

Therefore, the answer is C: 10.