What is oogenesis , Biology

Assignment Help:

What is Oogenesis ?

The female sex cells, or eggs, are formed in the ovaries, the primary sex organs of the female. The precursor of the egg cells, or oogonia, are formed during the prenatal development of the ovaries in the female embryo. However, the oogonia do not increase in number until after the third month of fetal development.

Oogonia divide by mitosis to form primary oocytes. These cells gradually die off, but about 200,000 are left in each ovary at puberty (about 11 to 14 years of age). Over the course of a woman's reproductive life, only about 450 oocytes will mature completely into eggs.

The primary oocyte begins meiosis, undergoing a very unequal division in which the larger cell becomes a secondary oocyte, and the other forms the first polar body, which eventually dies off. The second meiotic division, also unequal, forms a haploid ootid and a second polar body that also dies off. What is left is a single haploid egg cell or ovum (plural ova) that is 75,000 times larger than a sperm cell. The ovum contains contains proteins, lipids, and other raw materials for development. It is thought that the reason 3 of the 4 cells that result from meiosis die off is to provide the one surviving egg with sufficient resources for development.

 


Related Discussions:- What is oogenesis

Slow moving waters - biota of rivers, Slow Moving Waters - Biota of Rivers ...

Slow Moving Waters - Biota of Rivers The habitat of a slowly moving part of the river is very different from the one just described. Here the water flow is comparatively slow

Illustrate about heart, Heart Heart is a cone shaped muscular structur...

Heart Heart is a cone shaped muscular structure situated between two lungs in the thoracic cavity. It is covered by a sac like structure known as pericardium which has two lay

Pre-mating isolating mechanisms, We mentioned earlier that pre-mating mecha...

We mentioned earlier that pre-mating mechanisms are concerned with the prevention of occurrence of interspecific crosses. In such cases, a) the potential mates do not meet in wh

Succession, why succession more likely to occur on valley floor than steep ...

why succession more likely to occur on valley floor than steep slopes

What is the normal duration of the menstrual cycle, Q. What is the normal d...

Q. What is the normal duration of the menstrual cycle? How does the calendar contraceptive method work? The normal duration of the menstrual cycle is 28 days but it can vary am

What are the main human degenerative diseases, What are the main human dege...

What are the main human degenerative diseases? The main human degenerative diseases are separated into three groups: cardiovascular diseases, neoplastic diseases and degenerat

ASSINMENT, HISTORY ON CLASSIFICATION IN BIOLOGY

HISTORY ON CLASSIFICATION IN BIOLOGY

List the counselling skills, Q. List the counselling skills? Slowly sta...

Q. List the counselling skills? Slowly start winding up the contact with the client and the family by providing them support, motivating the client to take care of oneself with

Major events during gastrulation, MAJOR EVENTS DURING GASTRULATION - 1....

MAJOR EVENTS DURING GASTRULATION - 1.       There is rearrangement of cells due to morphogenetic movement of the cells of blastoderm. 2.       The three primary germ layer g

Respiration, explain the respiration that takes place in different organism...

explain the respiration that takes place in different organisms??

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd