Red Eye Allele in Fruit Flies - Dominance Explained

What’s inside this PDF?

Question: 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?

Options:

0%
25%
50%
100%

Correct Answer: 0%

Solution:

The cross RR x Rr will produce all red-eyed offspring (100% R). Thus, 0% will have white eyes.

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?

0%
25%
50%
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.

Mendelian Genetics – Understanding dominant and recessive alleles, and how they affect phenotypic ratios in offspring.
Genotype and Phenotype – Differentiating between the genetic makeup (genotype) and the observable traits (phenotype) of organisms.
Punnett Square – Using a Punnett square to predict the genotypes and phenotypes of offspring from a genetic cross.

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

What’s inside this PDF?

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

Practice Questions

Questions & Step-by-Step Solutions

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