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

Uterine torsion, Uterine Torsion Incidences of uterine torsions in cat...

Uterine Torsion Incidences of uterine torsions in cattle and buffaloes are not common. However, they are very common in heavy breeds and buffaloes and animals in slopy terrain

Morphology of angiosperms, define inflorescence and explain in detail about...

define inflorescence and explain in detail about it''s types

Define the stages of convaiescenca - nutrition during stress, Define the St...

Define the Stages of ConvaIescenca - Nutrition during Stress? This period of catabolism and alteration of the hormonal environment is known as the 'adrenergic - corticoid phase

What is endocytosis, Which of the following is true for endocytosis? A....

Which of the following is true for endocytosis? A. During endocytosis of GLUT4 transporters in fat cells, there is removal of GLUT4 transporters from plasma membranes. B. Du

Artificial selection, ARTIFICIA L SELECTION - Man selects the indiv...

ARTIFICIA L SELECTION - Man selects the individuals having the desired traits and separates them from those, which do not possess such characters. The selected ones are

Which is the other adnexal gland of the digestive system, Besides the liver...

Besides the liver which is the other adnexal gland of the digestive system that releases substances in the duodenum participating in extracellular digestion? The other adnexal

Medical surgical nursing, Medical Surgical Nursing: Medical Surgical N...

Medical Surgical Nursing: Medical Surgical Nursing refers to the  nursing care of adults who have  an actual or potential disorder of physiological functi~n.  The practice of

Functions of endoplasmic reticulum, FUNCTIONS OF E.R. (1 )      Mecha...

FUNCTIONS OF E.R. (1 )      Mechanical support - E.R. participates in formation of cytoskeleton with microfilaments, microtubules and intermediate filaments. (2 )

Hermaphroditism, Hermaphroditism You would have completely appreciated...

Hermaphroditism You would have completely appreciated now that sexual reproduction is definitely the more advanced type of reproduction. It gives for combination of genes from

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