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?

Answer 1

In a population of weasels where black (B) and white (W) are co-dominant traits, a heterozygous genotype (BW) produces black and white spotted weasels. If we are considering a cross of two heterozygous weasels (BW x BW), the Punnett square would look like this:

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

From this Punnett square, the possible genotypes of the offspring are:

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

This can be summarized as:

• 1 BB : 2 BW : 1 WW

Thus, the phenotypic ratio is:

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

In total, there are 4 phenotypes, with 1 being solid black. Therefore, the proportion of offspring that are black (BB) is \( \frac{1}{4} \) or 25%.

If there are 40 baby weasels born from this cross, we can calculate the expected number of black weasels as follows:

\[ \text{Number of black weasels} = \frac{1}{4} \times 40 = 10 \]

So, you should expect that 10 of the 40 baby weasels will be black.