Billy and Johnny are brothers, but they do not look alike. Which one of the following pairs of factors contributed to this genetic variation?

A- Non-disjunction and mitosis.
B- Cytokinesis and cloning.
C- Crossing over and independent assortment.
D- Asexual reproduction and binary fission.

C- Crossing Over

Explanation:

Crossing over is essentially the gene shuffling and swapping around of genetic information.

A- is false because mitosis describes the building of nonsexual cells. So in terms of genetics, meiosis is the one you're looking for in this scenario.

B- Brothers are not clones.

D- Your parents had to have sex to produce a child. This is not Asexual.

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."