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

Explain false positive tests, Q. Explain False Positive Tests? As ST de...

Q. Explain False Positive Tests? As ST depression has been equated with CAD, patients with this finding who have less than a critical coronary narrowing has been called false p

What is spermatogenesis in human biology, What is Spermatogenesis in human ...

What is Spermatogenesis in human biology? The male sex cells, or sperm, are produced in the oval-shaped testes, the primary sex organs of the male reproductive system, in a pro

Show the process of gas exchange in mammals, Q. How is gas exchange done in...

Q. How is gas exchange done in mammals? Mammals breathe through lungs their respiration is pulmonary. Q. How is circulation characterized in mammals? Mammals present a

Are the xylem and the phloem made of living cells, Are the xylem and the ph...

Are the xylem and the phloem made of living cells? The cells that constitute the xylem ducts are dead cells killed by lignin deposition. The cells of the phloem are living

Protect a species from extinction, In what ways can we try to protect a spe...

In what ways can we try to protect a species from extinction? We can attempt to protect species from extinction by making it illegal to kill the threatened animals or uproot o

Cleavage and gastrulation, Cleavage and Gastrulation Eventually, one s...

Cleavage and Gastrulation Eventually, one spermatozoon fuses with the ovum to r restore the diploid genomic condition and activates all the potentials in the fertilized egg ce

Explain the sub-clinical protein energy malnutrition, Explain the Sub-clini...

Explain the Sub-clinical Protein Energy Malnutrition? You have already learnt that clinical forms of PEM represent only a small proportion of the total cases of PEM in a commun

Improvement of cereal proteins - mutual supplementation, Define Improvement...

Define Improvement of cereal proteins - Mutual supplementation? Improvement of cereal proteins: Cereals, in general, are limiting in lysine and threonine while legumes, milk, m

What is class polychetae - marine worms, What is Class Polychetae - Marine ...

What is Class Polychetae - Marine Worms? The polychaetes differ from the oligochaetes in several ways. The name itself suggests one of the differences. The prefix "poly" means

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