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

Sieve tubes, What are sieve tubes suited for translocation of food? a.bord...

What are sieve tubes suited for translocation of food? a.bordered pits b.no end walls c.bordered lumen and perforated cross walls D.no protoplasm

Relate the oxide layer and biocompatibility of titanium, Relate the oxide l...

Relate the oxide layer and biocompatibility of titanium. The compatibility of a metal with its host environment depends on its resistance to biodegradation and on the degree of

Define etiology - anorexia nervosa, Define Etiology - Anorexia Nervosa? ...

Define Etiology - Anorexia Nervosa? The exact cause of eating disorders is not known. It is multi factorial in origin in which the personality of the patient, family relationsh

Foods for phenylketonuria patient, Q. Foods for phenylketonuria patient? ...

Q. Foods for phenylketonuria patient? The majority of foods for a PKU patient should come from the bottom half of the pyramid. As you may have observed, this contains the pheny

Genetic reservoir - conservation of wildlife, Genetic Reservoir - Conservat...

Genetic Reservoir - Conservation of Wildlife  Despite the present and future economic and health importance to human beings, very little is known about most of the earth's 1.

What are the etiological agents of malaria, What are the etiological agents...

What are the etiological agents of malaria? The etiological agents of malaria are protozoans of the genus Plasmodium. There are four dissimilar types of plasmodia that cause ma

Do plants placed under an environment drier than the habitat, Do plants pla...

Do plants placed under an environment drier than the habitat where they are used to living have a reduction or an increase in the time during which their stomata remain open? I

Describe class diplopoda and chilopoda in detail, Describe Class Diplopoda ...

Describe Class Diplopoda and Chilopoda in detail? Members of the Subphylum Crustacea and the Subphylum Uniramia have one major characteristic in common. Both groups have biting

Define metabolic utilization of carbohydrates, Define Metabolic utilization...

Define Metabolic utilization of carbohydrates? Following absorption, the monosaccharides enter the portal circulation and are carried to the liver. Both galactose and fructose

What are the five dna polymerases, The Eukaryotic cells have five several D...

The Eukaryotic cells have five several DNA polymerases; α, β, γ, δ or ε. The DNA polymerases contained in replication of chromosomal DNA are α and δ. DNA polymerases β or ε are con

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