In a certain species of fruit flies, the allele for red eyes (R) is dominant ove

Practice Questions

Q1
In a certain species of fruit flies, the allele for red eyes (R) is dominant over the allele for white eyes (r). If two red-eyed flies, one homozygous (RR) and one heterozygous (Rr), are crossed, what percentage of the offspring will have white eyes?
  1. 0%
  2. 25%
  3. 50%
  4. 100%

Questions & Step-by-Step Solutions

In a certain species of fruit flies, the allele for red eyes (R) is dominant over the allele for white eyes (r). If two red-eyed flies, one homozygous (RR) and one heterozygous (Rr), are crossed, what percentage of the offspring will have white eyes?
  • Step 1: Identify the alleles for eye color. Red eyes are represented by 'R' (dominant) and white eyes by 'r' (recessive).
  • Step 2: Determine the genotypes of the parent flies. One parent is homozygous (RR) and the other is heterozygous (Rr).
  • Step 3: Set up the cross between the two parents: RR (homozygous) and Rr (heterozygous).
  • Step 4: Use a Punnett square to find the possible combinations of alleles in the offspring.
  • Step 5: Fill in the Punnett square: The first parent (RR) can only contribute 'R' alleles, and the second parent (Rr) can contribute either 'R' or 'r'.
  • Step 6: The possible offspring combinations are: RR (red eyes) and Rr (red eyes).
  • Step 7: Count the offspring: 50% will be RR and 50% will be Rr, so all offspring will have red eyes.
  • Step 8: Since there are no 'rr' combinations, 0% of the offspring will have white eyes.
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