To create a Punnett square for a genetic cross, we need to use the parental genotypes to determine the possible genotypes of their offspring.
In this scenario:
- The mother is heterozygous for dimples, which means her genotype is [tex]\( Dd \)[/tex].
- The father is homozygous for no dimples, so his genotype is [tex]\( dd \)[/tex].
We can draw the Punnett square by setting the alleles from one parent across the top and the alleles from the other parent down the side.
Here's a step-by-step solution:
1. Write the alleles for the mother [tex]\( Dd \)[/tex] along the top of the grid:
[tex]\[ D \quad d \][/tex]
2. Write the alleles for the father [tex]\( dd \)[/tex] along the side of the grid:
[tex]\[
\begin{array}{c}
d \\
d \\
\end{array}
\][/tex]
3. Fill in the squares by combining the alleles from the top and the side:
[tex]\[
\begin{array}{c|c|c}
& D & d \\
\hline
d & Dd & dd \\
\hline
d & Dd & dd \\
\hline
\end{array}
\][/tex]
So, the Punnett square for a cross between a heterozygous mother for dimples (Dd) and a homozygous no-dimples father (dd) will be:
[tex]\[
\begin{array}{|c|c|}
\hline Dd & dd \\
\hline Dd & dd \\
\hline
\end{array}
\][/tex]
This Punnett square shows that there are two possible genotypes for the offspring: [tex]\( Dd \)[/tex] (heterozygous) and [tex]\( dd \)[/tex] (homozygous recessive). The ratio of these genotypes is 1:1. Thus, half of the offspring will have dimples (since [tex]\( D \)[/tex] is dominant) and half will not have dimples (since both alleles are [tex]\( d \)[/tex]).
