One gamete is formed during:
Crossing over
Oogenesis
Spermatogenesis
Sexual reproduction

Oogenesis

Explanation:

Oogenesis is a process in female reproductive system in which a matured ovum is formed from egg cell.

In human reproductive system one mature ovum is produced from four haploid cells during meiosis. This ovum is very large and it unite with the sperm to produce zygote.

There are three stages of Oogenesis, the multiplication phase,the growth phase and maturation phase.

In the multiplication phase, the germinal cells divide to form oogonia. The oogonia multiply and form oocytes. The oocytes pass through the growth phase and mature to form ovum.

One gamete is formed during:

Spermatogenesis

Explanation:

This involves development of an haploid spermatozoa resulting from germ cell

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.