To solve this problem, we can use a Punnett square to determine the frequencies of the phenotypes (visible traits) in the offspring resulting from the cross between the two RrYy parents.
Parent Genotypes
Both parents are heterozygous for seed shape and seed color, so their genotypes are RrYy.
Possible Gametes
Each parent can produce four types of gametes:
- RY (Round, Yellow)
- Ry (Round, Green)
- rY (Wrinkled, Yellow)
- ry (Wrinkled, Green)
Punnett Square
We can create a Punnett square with the gametes from each parent:
\[ \begin{array}{c|c|c|c|c} & RY & Ry & rY & ry \ \hline RY & RRYY & RRYy & RrYY & RrYy \ \hline Ry & RRYy & RRyy & RrYy & Rryy \ \hline rY & RrYY & RrYy & rrYY & rrYy \ \hline ry & RrYy & Rryy & rrYy & rryy \ \end{array} \]
Offspring Phenotypes
Now we can analyze the resulting offspring from the Punnett square:
-
Round, Yellow (R_Y_):
- RRYY: 1
- RRYy: 2
- RrYY: 1
- RrYy: 2 Total = 6 Round, Yellow
-
Round, Green (R_yy):
- RRYy: 2
- RrYy: 2 Total = 2 Round, Green
-
Wrinkled, Yellow (rrY_):
- RrYY: 1
- RrYy: 2 Total = 3 Wrinkled, Yellow
-
Wrinkled, Green (rryy):
- rrYY: 1
- rrYy: 1 Total = 2 Wrinkled, Green
Summary of Phenotypes
- Round Yellow: 6
- Round Green: 2
- Wrinkled Yellow: 3
- Wrinkled Green: 1
Total = 6 + 2 + 3 + 1 = 12.
Fraction of Offspring with Round, Yellow Seeds
The fraction of offspring with round, yellow seeds: \[ \text{Fraction} = \frac{\text{Number of Round, Yellow}}{\text{Total Offspring}} = \frac{6}{16} = \frac{3}{8}. \]
However, let's double-check:
Total number of offspring types
By combinatorial genetics and mapping out, we find that 9 out of the 16 squares correspond to Round seeds (R_) and each combination gives 3 contributions leading to Yellow seeds (Y_). Thus:
The correct fraction for Round, Yellow seeds is indeed:
\[ \frac{9}{16}. \]
Final Answer
C) \( \frac{9}{16} \)
1 answer