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

Describe the theory of darwins, Describe the theory of Darwin's? Most s...

Describe the theory of Darwin's? Most scientists today accept the theory that living organisms have evolved according to the concept that was first proposed by Charles Darwin i

What are the functions of the cytoskeleton, As the name shows, the cytoskel...

As the name shows, the cytoskeleton is responsible for the supporting of the normal shape of the cell; it also acts as a facilitator for substance transport across the cell and for

Theory of evolution and its rival theories, what is the problem that the th...

what is the problem that the theory of evolution and its rival theories try to solve?

Why plant life cycle known as alternation of generation, Why is the plant l...

Why is the plant life cycle known as alternation of generations? The plant life cycle is called as alternation of generations because in this cycle there are two dissimilar for

Explain the function of muscular tissue, How can the presence, localization...

How can the presence, localization and function of muscular tissue in beings of the phylum Annelida be explained? In these beings there are a longitudinal muscular layer under

Explain progressive loss of the axonal myelin sheath, What are some disease...

What are some diseases characterized by progressive loss of the axonal myelin sheath? Multiple sclerosis is a severe disease caused by progressive destruction of the myelin she

How can we examine the chromosomes, Is it more indicated for a geneticist d...

Is it more indicated for a geneticist desiring to map the X chromosome of the mother of a given family (the researcher does not have access to her DNA, only access to the genetic m

What is dietary fibre, Q. What is Dietary fibre? Dietary fibre is defin...

Q. What is Dietary fibre? Dietary fibre is defined as plant polysaccharide resistant to hydrolysis by the digestive enzymes in the human intestinal tract. It includes: • Str

Intravenous drug abusers, The risk for IE among IV drug abusers, 2 to 5 per...

The risk for IE among IV drug abusers, 2 to 5 per cent per patient- year, is estimated to be several fold greater than that of patients with rheumatic heart disease or prosthetic v

Genes and chromosomes, The gene is a distinct portion of a cell's DNA. Gene...

The gene is a distinct portion of a cell's DNA. Genes are coded instructions for making all the body needs, mainly proteins. Human beings have about 25,000 genes. Researchers have

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