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:

1. First, recall the concept of true - breeding: A true - breeding organism is homozygous for a particular trait. For the straight - winged parent (dominant trait), since straight wings (let's represent the dominant allele as \(S\)) are dominant and it is true - breeding, its genotype is \(SS\). For the curly - winged parent (recessive trait, let's represent the recessive allele as \(s\)), since it is true - breeding, its genotype is \(ss\).
2. When we cross a \(SS\) (straight - winged) parent with a \(ss\) (curly - winged) parent, using the principle of Mendelian inheritance (specifically the law of segregation and law of independent assortment for monohybrid cross), the gametes from the \(SS\) parent will all have the \(S\) allele, and the gametes from the \(ss\) parent will all have the \(s\) allele.
3. When these gametes combine during fertilization, the offspring (\(F_1\) generation) will have the genotype \(Ss\). This means that each offspring will have one allele (\(S\)) for straight wings and one allele (\(s\)) for curly wings.

• Let's analyze the other options:
• Option 1: The offspring will have the genotype \(Ss\), not two genes for straight wings (\(SS\)). So this option is incorrect.
• Option 2: The offspring with genotype \(Ss\) will produce gametes with either \(S\) (for straight wings) or \(s\) (for curly wings), not only gametes with genes for curly wings. So this option is incorrect.
• Option 4: The offspring has two different alleles (\(S\) and \(s\)) for the wing - type gene, not only one kind of allele. So this option is incorrect.

Answer:

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