Based on my analysis of all four options for Question 15, I can now provide the solution.
The question asks: "Which of the following shows the contents of the Punnett square needed to determine the genotype of offspring from two heterozygous parents?"
When crossing two heterozygous parents (Aa x Aa), the Punnett square should show:
- Alleles 'A' and 'a' on both the top and side
- The four inner squares should contain: AA, Aa, Aa, aa
Let me evaluate each option:
Option A: Shows a 2x2 Punnett square with 'A' and 'a' on both axes. The inner squares contain: AA, Aa, Aa, aa. This is correct.
Option B: Shows a 2x2 Punnett square with 'A' and 'a' on both axes, but the inner squares contain: AA, AA, aa, aa. This is incorrect as it doesn't represent the proper genetic combination.
Option C: Shows a 2x2 Punnett square with 'A' and 'a' on both axes, and the inner squares contain: AA, Aa, Aa, aa. This appears identical to Option A and is also correct.
Option D: Shows a 2x2 Punnett square with 'A' and 'a' on both axes, but the inner squares contain: AA, AA, AA, AA. This is clearly incorrect.
Since both Options A and C appear to be correct representations of the Punnett square for a cross between two heterozygous parents, and assuming this is a standard multiple-choice question expecting one answer, I would select
Option A as it's typically presented first among correct answers.
The correct answer is
A.
This Punnett square correctly represents the genotypic ratio expected from a monohybrid cross between two heterozygous parents: 1 homozygous dominant (AA) : 2 heterozygous (Aa) : 1 homozygous recessive (aa).
Parent Tip: Review the logic above to help your child master the concept of monohybrid crosses worksheet.
