Question

Round seeds and yellow seed color are dominant to wrinkled seeds and green seed color. Which Punnett square represents the correct way to set up the cross RRYy ´ RrYY?

Answer 1

The law of independent assortment tells us that the gametes will be distributed as \(RY\) and \(Ry\) in the first parent, with two copies of each: \(\color{red}R\color{blue}RYy~\implies~\{\color{red}RY,\color{blue}RY,\color{red}Ry,\color{blue}Ry\}\).

Similarly, for the second parent you get gametes with the following allele combinations: \(Rr\color{red}Y\color{blue}Y~\implies~\{R\color{red}Y,R\color{blue}Y,r\color{red}Y,r\color{blue}Y\}\).

Knowing this, you can set up the headings of the square as
\[\begin{array}{c|c|c}
&RY&RY&Ry&Ry\\
\hline
RY\\
\hline
RY\\
\hline
rY\\
\hline
rY
\end{array}\]