A wild-type Drosophila male and female are crossed, producing 324 female progeny and 161 male progeny. All their progeny are wild type.

Propose a genetic hypothesis to explain these data.

Verified step by step guidance

1. span>Step 1: Understand the genetic background of Drosophila. In Drosophila melanogaster, the wild-type phenotype is typically dominant, and sex determination is based on the X and Y chromosomes.</span
2. span>Step 2: Consider the sex determination mechanism. In Drosophila, females are XX and males are XY. The presence of two X chromosomes results in a female, while one X and one Y chromosome result in a male.</span
3. span>Step 3: Analyze the progeny ratio. The progeny consists of 324 females and 161 males, which suggests a deviation from the expected 1:1 sex ratio.</span
4. span>Step 4: Propose a hypothesis. The deviation from the expected 1:1 ratio could be due to a genetic factor affecting the viability of male progeny, such as a recessive lethal allele on the X chromosome that is masked in females (XX) but expressed in males (XY).</span
5. span>Step 5: Consider alternative explanations. Other factors, such as environmental influences or genetic linkage, could also contribute to the observed sex ratio, but the presence of a sex-linked lethal allele is a plausible genetic hypothesis.</span

Key Concepts

Sex-linked Inheritance

In Drosophila, certain traits are often linked to sex chromosomes, particularly the X chromosome. Males have one X and one Y chromosome, while females have two X chromosomes. If a trait is sex-linked, it can exhibit different inheritance patterns in males and females, which is crucial for understanding the progeny ratios observed in the cross.

Wild-type Phenotype

The wild-type phenotype refers to the most common or typical form of a trait found in a natural population. In this case, all progeny being wild type suggests that the alleles for the traits being studied are dominant or that the wild-type allele is present in both parents, leading to the expression of the wild-type phenotype in all offspring.

Progeny Ratio Analysis

Analyzing the ratio of male to female progeny can provide insights into the genetic mechanisms at play. In this scenario, the ratio of 324 females to 161 males suggests a potential sex-linked inheritance pattern, as the expected ratio for a typical Mendelian cross would be 1:1 for male and female offspring, indicating that the trait may be influenced by the sex chromosomes.