Meiosis, Biology

Assignment Help:

MEIOSIS

Every  organism is mortal, It  becomes  old and wornout  with advancing age  (= ageing )  and ultimately dies ,Before  death   however  ,it reproduces its own  kind, so that its  race  species  continues, Many  protozoan and some   lower metazoans  reproduce  asexually by  mitosis .Inheritance in these  is obviously uniparental  some  protozoans  and most  metazoans  perpetuate  their species by sexual  reproduction     . Inheritance in these  is therefore  biparental,  because  reproduction  involves union  of two sex  cells or gametes ( male gametic  cell or  sperm and femal gametic cells or  ovum),  producing  a single cells called  zygote, from  the zygote , then  arises the  entire  multicellular  body  of a new   progeny by its  repeated mitotic  division  and different   iation  of resultant cells  into the  different  types.

If  the gametes  were diploid  like all  body (= somatic) ,cell the zygote  would have  twice the  number  of  diploid  chromosomes  (tetraploid -4 x or 4n  and the  number would  go on multiplying  in that  order generation after  generation .No  species can survive  if  its  karyotype multiplies  in this  way, Hence  to prevent  this  situation ,sex  cells  or gametes are made  to possess a single  set of chromosomes  i.e. only  half  the number  of chromosomes  present  in the  karyotpye  ,This  single  set  is  called  haploid  or monoploid  (x or n)  gametic set  in contrast to  the  diploid  ( 2x or 2n)   karyotypic  or somatic set of chromosomes .

The  haploid  sex cells  are formed insexual organs i.e. gonads (testes in males  and ovaries in females ) from  diploid  germinal cells  by a specialized process  called  gametogenesis  (spermatogenesis   in  males and oogenesis  in females)  This process  necessarily involves a single  duplication of chromosomes  but two  consecutive  cell  division. The  second  division is mitotic  but the first  one is a special  type  of  reduction cell  division  called meiosis  (Gr meioum  =to diminish ) which  bring  about  the aforesaid reduction in chromosomal  number  to half  in the  resultant gametes .  Conventionally , the two  division  are designated as  first and second  meiosis.


Related Discussions:- Meiosis

Explain adverse effects of fungal prophylaxis, Adverse effects of Fungal Pr...

Adverse effects of Fungal Prophylaxis - Micafungin is generally well tolerated. Adverse events have included fever, headache, nausea, vomiting, diar-rhea, leukopenia, hepatic e

Is the edible part of the onion a fruit, Are fruits always the flesh part o...

Are fruits always the flesh part of the "fruits"? Is the edible part of the onion a fruit? In some so-called fruits the actual fruit is not the flesh part. For instance, the fl

Define pasteurization and sterilization - thermal processing, Define Pasteu...

Define Pasteurization and Sterilization - thermal processing? Pasteurization: Pasteurization is a mild heat treatment to kill part of the microorganisms present in food

Define clinical assessment for vitamin a, Define Clinical Assessment For Vi...

Define Clinical Assessment For Vitamin A? Clinical features of deficiency occur as ocular and extra ocular lesions. Ocular lesions affect the posterior segment of the eye init

State the terms - blastocoel and blastopore, State the terms - Blastocoel a...

State the terms - Blastocoel and Blastopore? During the development of embryo, single cells divide and form a hollow ball of cells one cell layer thick. Cavity inside this holl

Define seminal plasma in human male, Seminal plasma in human males is rich ...

Seminal plasma in human males is rich in : 1. fructose and calcium 2. glucose and calcium 3. DNA and testosterone 4. ribose and potassium Fructose and Calcium

Determine about the colloblast cell, Determine about the Colloblast cell? ...

Determine about the Colloblast cell? The unique sticky discharge cells found in the tentacles of ctenophorans. They are used to capture prey, and although cnidoblasts resemble

What are the functions of the osseous tissue, Q. What are the functions of ...

Q. What are the functions of the osseous tissue? The main functions of the osseous tissue that are to provide structural rigidity to the body and to delineate the spatial posit

What is the gel electrophoresis, Which of the following is a false stateme...

Which of the following is a false statement regarding gel electrophoresis? A. An electric current is used in order move DNA fragments by a semi-porous gel. B. Fragments of n

Define protein requirement during tuberculosis, Define Protein requirement ...

Define Protein requirement during tuberculosis Protein : Achronic infection  is marked by a prolonged duration of fever. This leads to wasting of muscles, increased nitrogen

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