When a true-breeding pea plant that produces yellow round seeds (YYRR) is crossed with a true-breeding pea plant that produces green wrinkled seeds (yyrr), all of the F1 offspring produce yellow round seeds. What fraction of the offspring of a F1 X F1 cross is predicted to produce green round seeds? Group of answer choices
Question
When a true-breeding pea plant that produces yellow round seeds (YYRR) is crossed with a true-breeding pea plant that produces green wrinkled seeds (yyrr), all of the F1 offspring produce yellow round seeds. What fraction of the offspring of a F1 X F1 cross is predicted to produce green round seeds? Group of answer choices
Solution
The question is asking about a classic Mendelian genetics problem. Here's how to solve it:
Step 1: Identify the genotypes of the parent plants. The yellow round seed plant is YYRR and the green wrinkled seed plant is yyrr.
Step 2: Determine the genotype of the F1 generation. Since each parent can only pass on one allele for each trait, all F1 offspring from this cross will be YyRr.
Step 3: Set up a Punnett square for the F1 x F1 cross. This is a dihybrid cross, so it's a bit more complex. The Punnett square will have 16 boxes.
Step 4: Fill in the Punnett square. Remember, each parent can pass on one of two alleles for each trait. So, for example, one parent could pass on YR, Yr, yR, or yr.
Step 5: Count the number of boxes that correspond to green round seeds. The genotype for green round seeds is yyR_. The underscore indicates that we don't care what the second allele is - it could be R or r.
Step 6: Divide the number of boxes with yyR_ by the total number of boxes to get the fraction of offspring predicted to produce green round seeds.
When you do this, you'll find that 2 out of the 16 boxes have the genotype yyR_, so the predicted fraction of offspring that produce green round seeds is 2/16 or 1/8.
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