An insect species is discovered in which the heterogametic sex is unknown. An X-linked recessive mutation for reduced wing (rw) is discovered. Contrast the F₁ and F₂ generations from a cross between a female with reduced wings and a male with normal-sized wings when the male is the heterogametic sex.

Key Concepts

X-linked Inheritance

X-linked inheritance refers to the pattern of inheritance for genes located on the X chromosome. In this case, the reduced wing mutation (rw) is recessive and linked to the X chromosome. Males, having one X and one Y chromosome, will express the trait if they inherit the X chromosome carrying the mutation, while females, with two X chromosomes, must inherit two copies of the mutation to express the trait.

Heterogametic Sex

The heterogametic sex is the sex that produces two different types of gametes regarding sex chromosomes. In many species, including insects, males are heterogametic (XY), while females are homogametic (XX). Understanding which sex is heterogametic is crucial for predicting the inheritance patterns of X-linked traits, as it determines how mutations will be passed on to offspring.

F₁ and F₂ Generations

The F₁ generation is the first filial generation resulting from a cross between two parental (P) individuals, while the F₂ generation is produced by interbreeding individuals from the F₁ generation. In this scenario, analyzing the phenotypes of the F₁ and F₂ generations will reveal how the X-linked recessive trait for reduced wings is expressed, depending on the sex of the offspring and the inheritance of the X-linked mutation.