Question

scientists often experiment with brassica plants because brassica plants grow very fast, and they produce seeds 30 days after being planted. this quick maturation allows scientists to study several generations in a short time. usually the scientists use brassica plants to study genetics and inheritance.
in one investigation that studied the inheritance of brassica stem color, scientists crossed a heterozygous dominant (rr) plant with a homozygous recessive (rr) plant. this resulted in offspring with purple stems (rr) and offspring with green stems (rr). a punnett square for this cross is shown below.
you may use the calculator.
type your answers in the boxes.
what percent of the offspring will have green stems?
what percent of the offspring will have purple stems?

Explanation:

Step1: Fill in the Punnett square

The Punnett square has \(R\) and \(r\) from the heterozygous dominant (\(Rr\)) parent along the top, and \(r\) and \(r\) from the homozygous recessive (\(rr\)) parent along the side.
The four cells of the Punnett square will be \(Rr\), \(rr\), \(Rr\), \(rr\).

Step2: Determine the phenotypes

Since \(R\) (purple) is dominant over \(r\) (green), \(Rr\) has purple stems and \(rr\) has green stems.
Out of 4 offspring, 2 are \(Rr\) (purple) and 2 are \(rr\) (green).

Answer:

Green stems: \(50\%\)
Purple stems: \(50\%\)