The following figure illustrates reciprocal crosses involving chickens with sex-linked dominant barred mutation. For Cross A and for Cross B, cross the F₁ roosters and hens and predict the feather patterns of roosters and hens in the F₂.

Verified step by step guidance

1. Step 1: Understand the genetic basis of the trait. Since the barred mutation is sex-linked and dominant, it is located on the Z chromosome (chickens have ZW sex determination, where males are ZZ and females are ZW). The barred allele (B) is dominant over the non-barred allele (b).
2. Step 2: Identify the genotypes of the F₁ roosters and hens from Cross A and Cross B. Use the information from the reciprocal crosses to determine which parent contributed which allele, keeping in mind that males have two Z chromosomes (ZZ) and females have one Z and one W chromosome (ZW).
3. Step 3: Set up Punnett squares for the F₁ crosses. Since males are ZZ and females are ZW, the male contributes one Z chromosome to all offspring, while the female contributes either a Z or a W chromosome. Use the genotypes of the F₁ parents to determine the possible allele combinations in the F₂ generation.
4. Step 4: Predict the phenotypes of the F₂ offspring by considering the dominance of the barred allele. For males (ZZ), having at least one B allele will result in barred feathers; for females (ZW), having the B allele on the single Z chromosome will result in barred feathers, while the W chromosome does not carry this gene.
5. Step 5: Summarize the expected feather patterns in the F₂ generation for both roosters and hens, indicating the proportion of barred and non-barred individuals based on the genotypic ratios derived from the Punnett squares.

Key Concepts

Sex-Linked Inheritance

Sex-linked inheritance refers to genes located on sex chromosomes, typically the X chromosome in chickens. Traits linked to these chromosomes show different inheritance patterns in males and females because males have one X and one Y chromosome, while females have two X chromosomes.

Dominant and Recessive Alleles

Dominant alleles express their trait even if only one copy is present, while recessive alleles require two copies to be expressed. In sex-linked dominant mutations, a single copy of the mutant allele on the X chromosome causes the trait to appear in both males and females.

Reciprocal Crosses and Predicting F2 Phenotypes

Reciprocal crosses involve switching the sexes of the parents with specific traits to study inheritance patterns. Predicting F2 phenotypes requires understanding how alleles segregate and combine in offspring, considering sex linkage and dominance to determine the expected feather patterns in male and female progeny.