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:

Let's assume the allele for straight wings is \(S\) (dominant) and for curly wings is \(s\) (recessive). A true - breeding straight - winged parent has the genotype \(SS\), and a true - breeding curly - winged parent has the genotype \(ss\).
When \(SS\times ss\) (using Punnett square principles or Mendelian genetics of single - gene crosses), the \(F_1\) generation is obtained by combining gametes. The \(SS\) parent can only produce gametes with \(S\), and the \(ss\) parent can only produce gametes with \(s\).
So, the \(F_1\) generation will all have the genotype \(Ss\). This means each offspring has one allele for straight wings (\(S\)) and one allele for curly wings (\(s\)).

• The first option: Offspring do not have two genes for straight wings. Since one parent contributes \(s\) (from curly - winged parent), this is wrong.
• The second option: Offspring with genotype \(Ss\) will not produce only gametes with \(s\). They can produce gametes with \(S\) and \(s\), so this is wrong.
• The fourth option: Offspring have two different alleles (\(S\) and \(s\)) for the wing - type gene, so this is wrong.

Answer:

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