The physical process that makes gene linkage incomplete is

A. segregation

B. mitosis

C. the lining up of chromosomes in the middle of the cell

D. cyclin reaching a threshold concentration

E. crossing over

Option E, Crossing Over

Explanation:

In the process of crossing over, a chromosome is replicated to produce two sister chromatids.

Sister chromatids have genes that are divided and shared with the offspring in equal number. In this way genetic traits are exchanged and the offspring has a new set of genes.

This process takes place at the prophase stage of cell division.

Without crossing over, gene linkage is incomplete.

Hence, option E is correct