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

Can you explain reticulum and the rumen, Q. Cows swallow their food once an...

Q. Cows swallow their food once and then this food goes back to the mouth to be chewed again. How can this phenomenon be explained? The food ingested by cows and other ruminant

Explain differential staining technique, Explain Differential Staining Tech...

Explain Differential Staining Technique? It divides bacteria into separate groups based on staining properties, like Gram's stain, Acid-fast stain etc. Here 2 or more contrasti

Therapeutic dose of pyridoxine, Q. Therapeutic dose of pyridoxine? Ther...

Q. Therapeutic dose of pyridoxine? Therapeutic dose of pyridoxine (lg/day) is usually tried in all patients with hypermethioninernia and homocystinemia. For patients who do not

Why is quarrantine introduction of a plant species, Why is quarrantine a mu...

Why is quarrantine a must before introduction of a plant species from a dissimilar country? a) What is meant by apoplast pathway? Why does it occur in cortex and not in endoder

Explain sickle cell anemia, Explain Sickle cell anemia If 4% of a peopl...

Explain Sickle cell anemia If 4% of a people are born with a severe form of sickle cell anemia. what percent of population will be resistant to malaria in spite of carrying

Respiration in scorpion or spider, RESPIR A TIO N IN SCORPION OR SPIDER ...

RESPIR A TIO N IN SCORPION OR SPIDER - Respiratory organs are book lungs. A book lung is a chamber containing a series of thin, vascular, parallel lamellae arranged li

Types of cells in phloem, Types of cells in Phloem The phloem consists...

Types of cells in Phloem The phloem consists of 4 types of cells: i).sieve elements, ii) companion cells, iii) phloem parenchyma and sometimes iv) phloem fibres. The metabolit

First systematic theory in psychiatric nursing, First Systematic Theory in ...

First Systematic Theory in Psychiatric Nursing: Hildegard Peplau, one of the nurse-theorist, published a book on Interpersonal Relations  in Nursing (1952) and gave-the introd

Signs and symptoms of acute glomerulonephritis, Signs and Symptoms ...

Signs and Symptoms Decreased urine output  Bloody or brown colour urine  Edema Malaise  Mild headache  Gastrointestinal disturbances

Nucleic acid hybridization, Nucleic acid thermodynamics is the learning of ...

Nucleic acid thermodynamics is the learning of how temperature affects the nucleic acid structure of dsDNA (double-stranded DNA). The melting temperature (Tm) is explained as the t

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