Which of the following best describes how crossing over occurs during meiosis?

a. during prophase i, homologous chromosomes are lined up and pulled apart to opposite poles.
b. during prophase ii, sister chromatids trade places with each other before
metaphase begins.
c. during prophase i, segments of chromatids are exchanged between homologous chromosomes.
d. during prophase ii, chromosomes overlap and sections of each chromosome switch places.

The correct option is C)  During prophase I, segments of chromatids are exchanged between homologous chromosomes.

Explanation:

Meiosis can be described as a process of cell division which leads to genetic variations. These variations are produced due to crossing over and independent assortment of chromosomes. The number of chromosomes is reduced to half as the parent cells during this type of cell division.

Crossing over occurs between prophase I and metaphase I. During prophase I, segments of chromatids are known to be exchanged between the homologous chromosomes. Hence, option C is correct.

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%