The assertion is correct. In Morgan’s experiments on Drosophila, genes located close together on the same chromosome showed tight linkage and hence very low recombination frequency, because crossing over between them is less likely.

The reason is also correct. In fruit flies, sex determination depends on X and Y chromosomes; fertilization by an X-bearing sperm produces a female (XX), while Y-bearing sperm produces a male (XY).

However, this reason is not related to gene linkage or recombination. It describes sex determination, not the cause of tight linkage.