Crossing over occurs in prophase of meiosis I. Crossing over results in A. half the number of original chromosomes. B. double the number of original chromosomes. C. genetically identical homologous chromosomes. D. new combinations of genes.

New combinations of genes.

Explanation:

Crossing over may be defined as the process of the exchange of the genetic material of the homologous chromosomes between non sister chromatids. The crossing over occurs in the prophase of the meiosis.

The some portion of genetic material exchanges randomly on the crossing over. This causes the generation of the new combination of genes in the organism. The linked chromosomes shows crossing over between them.

Thus, the correct answer is option (D).

D. new combinations of genes.