Question

a scientist is studying fruit fly wings. straight wings are dominant, and curly wings are recessive. which statement correctly describes the f₁ generation if a straight - winged parent is crossed with a curly - winged parent and if both parents are true breeding?
○ the offspring will have two genes for straight wings.
○ the offspring will produce only gametes that have genes for curly wings.
○ the offspring will have one allele for straight wings and one allele for curly wings.
○ the offspring will have only one kind of allele for the gene that determines wing type.

Explanation:

Step1: Recall True - Breeding and Alleles

True - breeding organisms are homozygous for a trait. Let's represent the allele for straight wings as \( S \) (dominant) and the allele for curly wings as \( s \) (recessive). The straight - winged true - breeding parent will have a genotype of \( SS \), and the curly - winged true - breeding parent will have a genotype of \( ss \).

Step2: Analyze the Cross

When we cross a \( SS \) (straight - winged, true - breeding) parent with a \( ss \) (curly - winged, true - breeding) parent, using the principles of Mendelian genetics (specifically, the law of segregation and the law of dominance), the \( SS \) parent will produce gametes with the \( S \) allele, and the \( ss \) parent will produce gametes with the \( s \) allele.
When these gametes combine during fertilization, the offspring (\( F_1 \) generation) will have a genotype of \( Ss \).

Step3: Evaluate Each Option

• Option 1: The offspring has a genotype of \( Ss \), not \( SS \), so it does not have two genes for straight wings. Eliminate this option.
• Option 2: The offspring with genotype \( Ss \) will produce two types of gametes, those with the \( S \) allele (for straight wings) and those with the \( s \) allele (for curly wings), not only gametes with the \( s \) allele. Eliminate this option.
• Option 3: The offspring with genotype \( Ss \) has one allele (\( S \)) for straight wings and one allele (\( s \)) for curly wings. This is correct.
• Option 4: The offspring has two different alleles (\( S \) and \( s \)) for the wing - type gene, not only one kind of allele. Eliminate this option.

Answer:

The offspring will have one allele for straight wings and one allele for curly wings.