To determine the expected ratio of yellow seeds to green seeds when crossing two pea plants with the genotype [tex]\( Yy \times Yy \)[/tex], we can use a Punnett square to explore all possible combinations of the alleles they can pass to their offspring.
Let's solve this step-by-step:
1. Identify the alleles for each parent:
Each parent has the genotype [tex]\( Yy \)[/tex], meaning they have one dominant allele [tex]\( Y \)[/tex] for yellow seeds and one recessive allele [tex]\( y \)[/tex] for green seeds.
2. Set up the Punnett square:
The Punnett square helps visualize how the alleles can combine:
[tex]\[
\begin{array}{c|c|c}
& Y & y \\
\hline
Y & YY & Yy \\
\hline
y & Yy & yy \\
\end{array}
\][/tex]
3. Fill in the Punnett square:
- The top row and left column represent the alleles from each parent.
- In each cell, we combine one allele from the parent on the top row with one allele from the parent on the left column.
The completed Punnett square shows the possible genotypes for the offspring:
[tex]\[
\begin{array}{c|c|c}
& Y & y \\
\hline
Y & YY & Yy \\
\hline
y & Yy & yy \\
\end{array}
\][/tex]
4. Determine the genotypes and their corresponding phenotypes:
- [tex]\( YY \)[/tex] (Yellow)
- [tex]\( Yy \)[/tex] (Yellow)
- [tex]\( Yy \)[/tex] (Yellow)
- [tex]\( yy \)[/tex] (Green)
There are four possible genotypes, and their phenotypic expression will be:
- 1 [tex]\( YY \)[/tex] for yellow seeds
- 2 [tex]\( Yy \)[/tex] for yellow seeds
- 1 [tex]\( yy \)[/tex] for green seeds
5. Count the number of each phenotype:
- Yellow seeds: [tex]\( YY \)[/tex] and [tex]\( Yy \)[/tex]
- 1 [tex]\( YY \)[/tex]
- 2 [tex]\( Yy \)[/tex]
Total yellow seeds = 3
- Green seeds: [tex]\( yy \)[/tex]
Total green seeds = 1
6. Calculate the ratio of yellow seeds to green seeds:
The ratio of yellow seeds to green seeds is [tex]\( 3 : 1 \)[/tex].
Thus, the correct answer is:
C. [tex]\( 3: 1 \)[/tex]
