Question

in pigeons, the z and w chromosomes determine the gender of offspring. male pigeons have two z chromosomes, female pigeons have one z chromosome and one w chromosome. the gene for feather color is carried only on the z chromosome. there are three alleles for feather color: ash red, blue, and brown. the ash - red allele is dominant to blue allele and to the brown allele. the blue allele is also dominant to the brown allele. a male pigeon with one blue and one brown allele mates with a female pigeon with ash - red feathers. what percentage of their offspring are expected to have ash - red feathers?
0% of females and 100% of males
25% of females and 75% of males
50% of females and 50% of males
100% of females and 0% of males

Explanation:

Step1: Determine Genotypes

Male pigeon: \( Z^B Z^b \) (blue and brown alleles on Z chromosomes). Female pigeon: \( Z^A W \) (ash - red allele on Z, W chromosome).

Step2: Analyze Offspring Genotypes

• Male offspring: Get one Z from male (\( Z^B \) or \( Z^b \)) and one Z from female (\( Z^A \)). So genotypes: \( Z^A Z^B \), \( Z^A Z^b \). Both have ash - red (since \( Z^A \) is dominant).
• Female offspring: Get Z from male (\( Z^B \) or \( Z^b \)) and W from female. Genotypes: \( Z^B W \), \( Z^b W \). Neither has ash - red (needs \( Z^A \), which they don't get from female as female gives W to females).

Step3: Calculate Percentages

• Females with ash - red: 0%.
• Males with ash - red: 100% (since all male offspring have \( Z^A \) from female, leading to ash - red phenotype).

Answer:

0% of females and 100% of males (the first option in the list, e.g., if it's option A: A. 0% of females and 100% of males)