Spermatocytogenesis, Biology

Assignment Help:

SPERMATOCYTOGENESIS

In this process four spermatid develop from one PGC.

(i) Multiplication phase

  1. The spermotogonia or sperm mother cells lie next to the basement membrane.
  2. These divide repeatedly by mitosis producing new sex cells.
  3. Some of these cells move towards the lumen of the seminiferous tubule and enter the growth phase.
  4. These are called primary spermatocytes while others produced by the mitotic division of spermatogonia remain in the original condition and continue to produce new spermatogonia throughout the reproductive life of the animal.

(ii) Growth phase

  1. The spermatogonia, formed as a result of repeated divisions of the primordial germ cells, stop dividing and prepare themselves for maturation division.
  2. They increase in size by accumulating nourishing material obtained from germinal cells.
  3. The enlarged cells are known as primary spermatocytes.
  4. Initially, the nucleus of each primary spermatocyte is of ordinary size, but soot it imbides material and enlarges considerably.
  5. At the end of growth phase, when the primary spermatocyte is ready to undergo first maturation division (i.e. the reduction division) its nucleus is much larger than that spermatogonial cell.

(iii) Maturation phase

  1. Each diploid primary spermatocyte undergoes the first maturation division which is a reduction division, with its long drawn out and complicated prophase.
  2. The pairing and spliting of homologons chromosomes take place during zygotene and pachytene and this leads to the formation of tetrads. Due to crossing over, the exchange of homologus chromosomes also take place.
  3. According to some, all these chromosomal events are completed in the growth phase only, so that during first maturation division the chromosomes are equally distributed to the two daughter cells.
  4. As a result of reduction division, the two cells formed are haploid. These haploid cells are called secondary spermatocytes.
  5. The secondary spermatocytes undergo second maturation division which is a simple mitotic division.
  6. As a result, each secondary spermatocyte divides into two equal cells, called spermatids.
  7. In the end of maturation phase four haploid spermatids are formed from each, diploid primary spermatocyte.

Related Discussions:- Spermatocytogenesis

Determine the pre-conditions for gtt, Pre-conditions for GTT You are ad...

Pre-conditions for GTT You are advised to carry out the GTT (OGTT) test to confirm a diagnosis of diabetes mellitus for a person with: a) The history of glycosuria (glucose

Expression, To "express" a gene is to make it to function properly. A gene ...

To "express" a gene is to make it to function properly. A gene which encodes a protein will, when expressed, be transcribed or translated to produce that particular protein. A gene

The red data book, The Red Data Book Species judged as threatened are ...

The Red Data Book Species judged as threatened are listed by various agencies as well as by some private organisations. The most cited of these lists is the Red Data Book. It

Differences between continuous traits and discrete traits, Can you please d...

Can you please describe the differences between continuous traits and discrete traits and how it helps an ecologist measure variation? Please give a few examples.

What is reproductive isolation, What is reproductive isolation? The Liv...

What is reproductive isolation? The Living beings are considered under reproductive isolation when they cannot cross among themselves or if they can cross but cannot generate f

What is the type of circulatory system present in arthropods, What is the t...

What is the type of circulatory system present in arthropods? Do these animals have heart and respiratory pigments? In arthropods the respiratory system is open (lacunar). Blo

Explain ailing implant, Explain Ailing Implant Which may indicate an in...

Explain Ailing Implant Which may indicate an increased risk for failure, which can be of temporary significance or amenable to treatment and is generally a soft tissue aberrati

Illustrate the metabolic processes of vitamin B, Illustrate metabolic proce...

Illustrate metabolic processes of vitamin B In the human and animal metabolism, they form a functional unit, since, as components of the various coenzymes, they are essential

Types of fats, FATS ARE OF TWO TYPES (a) Hard Fats They are t...

FATS ARE OF TWO TYPES (a) Hard Fats They are true fats which are solid at room temperature of 20 o C. It is due to presence of long chain saturated fatty acid

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