Final answer:
Option (1), Genetic recombination does not occur in Drosophila males, which is true, because they are hemizygous carrying only one X chromosome.
Step-by-step explanation:
The statement genetic recombination does not occur in Drosophila males is true. In Drosophila, also known as fruit flies, males are hemizygous, meaning they have only one allele for any X-linked characteristic because they are XY. This is in contrast to females, which have two X chromosomes and are XX.
The process of genetic recombination, which involves the exchange of genetic material between homologous chromosomes during meiosis, does not typically occur in Drosophila males because they only have one X chromosome, and no pairing occurs between the X and Y chromosomes during meiosis. Therefore, the recombination of X-linked genes does not happen in males, while it does in females, where two X chromosomes are present.
Regarding the review questions, X-linked recessive traits are observed more frequently in males than females because males only have one X chromosome, so any recessive allele on that chromosome will be expressed. The recombination frequency that corresponds to perfect linkage and violates the law of independent assortment is 0, while the frequency that corresponds to independent assortment and the absence of linkage is 0.5. Thomas Morgan's 1912 experiments on Drosophila led to observations of recombination frequencies that were significant but less than 50%, suggesting linkage between certain genes.