In pea plants, the allele for round seeds is dominant to the allele for wrinkled seeds. At another gene locus, the allele for yellow seeds is dominant to the allele for green seeds... In pea plants, the allele for round seeds is dominant to the allele for wrinkled seeds. At another gene locus, the allele for yellow seeds is dominant to the allele for green seeds. These two allele pairs assort independently. If a plant breeder crosses one plant that has wrinkled seeds and is heterozygous for yellow seeds with a second plant that is heterozygous for both traits, what ratio of the plants will produce wrinkled, yellow seeds? (Enter the number only. For example, enter 1/16, 4/8, or 3/16) Read more

Steps to Solve

1. Identify the genotypes of the parent plants

Let’s assume that wrinkled seeds are represented by the allele $r$ (recessive) and yellow seeds by the allele $Y$ (dominant). The typical genotype for plants that produce round, yellow seeds would be $RRYY$ or $RrYY$, while those producing wrinkled, yellow seeds would have a genotype of $rrYY$ or $rrYy$. You'll need to identify the genotypes of the parent plants involved in the cross.

2. Set up the Punnett square

Assuming one parent is $RrYy$ (round yellow) and the other is $rryy$ (wrinkled yellow), we can set up a Punnett square to predict the genotypes of the offspring.

3. Calculate the genotypes from the Punnett square

Fill in the Punnett square by combining alleles from both parents.

The possible combinations will be:

• $RrYy$
• $Rryy$
• $rrYy$
• $rryy$

4. Determine phenotypes

Now, interpret the Punnett square results to determine which combinations will result in wrinkled yellow seeds. Since $Y$ is dominant over $y$, seeds with $rrYy$ and $rryy$ will both be wrinkled yellow.

5. Calculate the ratio of offspring

Now, count the total number of offspring that result in wrinkled yellow seeds and divide that by the total number of combinations in the Punnett square.

If $rrYy$ and $rryy$ count as producing wrinkled yellow seeds, you would have 2 out of 4 total offspring resulting in this phenotype.

Thus, the ratio is $$ \frac{2}{4} = \frac{1}{2} $$ or 1:2.