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

Venous system, VENOU S SYSTEM It is collecting system formed by the...

VENOU S SYSTEM It is collecting system formed by the uniting branches as smaller and then larger veins and venacava leading to the heart. Blood from anterior part of the

Zoonoses disease-campylobacteriosis, Campylobacteriosis The genus Camp...

Campylobacteriosis The genus Campylobacter has been long associated with the cause of veterinary diseases under different names. It is only in the last 30 years that these org

Indications for surgery-pulmonary regurgitation, Indications for Surgery : ...

Indications for Surgery : Patients usually present with fatigue, dyspnoea and ventricular arrhythmias. If they have additional tricuspid regurgitation, pulmonary valve replacement

Six kingdom worksheet, what protist changes shape constantly and flows arou...

what protist changes shape constantly and flows around its food to engulf it?

How is snow - blindness caused in humans, How is snow - blindness caused in...

How is snow - blindness caused in humans? a) Mention the site where syngamy happens in amphibians and reptiles correspondingly.

Chemolithoautotrophs - nutritional types of microorganisms, Explain Chemoli...

Explain Chemolithoautotrophs - Nutritional Types of Microorganisms These microorganisms use inorganic compound as source of energy and electron and CO 2 as a source of carbon.

Determine the method of recombination, Which of the following is a false st...

Which of the following is a false statement regarding the method of recombination or crossing-over? A. Crossing-over takes place during prophase I of meiosis B. Recombinatio

Define sporangiophore - types of hyphae, Define Sporangiophore - Types of H...

Define Sporangiophore - Types of Hyphae? Sporangiophore - Tufts of special, erect unbranched, hyphae growing in air arise from stolon just opposite to rhizoids. These are s

Explain about the term accommodation, Explain about the term accommodation....

Explain about the term accommodation. Normally, the human eye focuses at objects at infinity, without exerting any power. This implies that while a person is observing an objec

Explain nutritional and functional role of phosphates, Minerals :- Phosphat...

Minerals :- Phosphates Food Source      Ubiquitous, animal products tend to be good sources Nutritional Functional role Essential nutrient: Deficiency is rare due

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