Question

the punnett square shows the possible allele combinations that result from a dihybrid cross between pea plants. both pea plants are heterozygous for seed shape (round- r, and wrinkled- r) and pod color (green- y, and yellow- y)
which of the following conclusions can be reached about the offspring of this cross?
\bigcirc 9 round seed and green pods, 3 wrinkled seed and green pods, 3 round seed and yellow pods, 1 wrinkled seed and yellow pods
\bigcirc 100% round seed and green pod and 0% wrinkled seed and green pod
\bigcirc 1 round seed and green pods, 3 wrinkled seed and green pods, 3 round seed and yellow pods, 9 wrinkled seed and yellow pods
\bigcirc 50% round seeds and 50% wrinkled seeds, 50% green pods and 50% yellow pods

Explanation:

Step1: Count the number of each phenotype

• Round seeds (\(R-\)): \(12\) (count all genotypes with \(R\)).
• Wrinkled seeds (\(rr\)): \(4\).
• Green pods (\(Y-\)): \(12\) (count all genotypes with \(Y\)).
• Yellow pods (\(yy\)): \(4\).
• Calculate the proportion:
• For seed shape: \(\frac{12}{16}=\frac{3}{4}\) (round), \(\frac{4}{16}=\frac{1}{4}\) (wrinkled).
• For pod color: \(\frac{12}{16}=\frac{3}{4}\) (green), \(\frac{4}{16}=\frac{1}{4}\) (yellow).

Step2: Analyze each option

• Option 1: \(9\) wrinkled seed and yellow pods (\(rryy\)) is incorrect as there are \(1\) \(rryy\) (count in the Punnett square).
• Option 2: \(100\%\) round seed is incorrect as \(\frac{1}{4}\) are wrinkled.
• Option 3: \(50\%\) round and \(50\%\) wrinkled is incorrect as it's \(75\%\) - \(25\%\).
• Option 4: Count genotypes:
• \(RRYY: 1\), \(RRYy: 2\), \(RrYY: 2\), \(RrYy: 4\) (round - green).
• \(RRyy: 1\), \(Rryy: 2\) (round - yellow).
• \(rrYY: 1\), \(rrYy: 2\) (wrinkled - green).
• \(rryy: 1\) (wrinkled - yellow).
• So \(3\) round - green (\(R - Y-\)), \(3\) round - yellow (\(R - yy\)), \(1\) wrinkled - yellow (\(rryy\)), \(3\) wrinkled - green (\(rrY-\)) (by combining counts: for example, round - green (\(R - Y-\)) has \(1 + 2+2 + 4=9\) but proportionally in a \(16\) - box Punnett square, using the ratio \(9:3:3:1\) from dihybrid cross (\((RrYy\times RrYy)\) gives \(9\) \(R - Y-\): \(3\) \(R - yy\): \(3\) \(rrY-\): \(1\) \(rryy\)). Here, when counting actual genotypes in the given Punnett square (assuming it's a \(4\times4\) with correct dihybrid cross representation), we get \(9\) \(R - Y-\) (round - green), \(3\) \(R - yy\) (round - yellow), \(3\) \(rrY-\) (wrinkled - green), \(1\) \(rryy\) (wrinkled - yellow).

Answer:

9 round seed and green pods, 3 wrinkled seed and green pods, 3 round seed and yellow pods, 1 wrinkled seed and yellow pods.