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

Animal viruses, Chart of taxonomy of animal viruses

Chart of taxonomy of animal viruses

Contra indication in circulatory assist devices, Contra Indication :  It i...

Contra Indication :  It is absolutely contra indicated if their is more than trivial aortic regurgitation. Aortic aneurysm and severe aorto iliac disease are also contra indicatio

Can be made from set of 20 naturally occurring amino acids, How many differ...

How many different molecules composed of (A) two (B) three, and (C) four amino acids, linked together by peptide bonds, can be made from the set of 20 naturally occurring amino aci

Define vegetable as a rich source of protein, Define Vegetable as a rich so...

Define Vegetable as a rich source of protein? Fresh vegetables are not considered to be a very good source of proteins. On fresh weight basis, the average protein content of so

Consequences of air pollution, Consequences of Air Pollution The physi...

Consequences of Air Pollution The physiological effects of toxic pollutants on living beings can be of two types: Acute effects and Chronic effects. Acute effec

Define need of vitamin c during pregnancy period, Define need of vitamin C ...

Define need of vitamin C during pregnancy period? Vitamin C deficiency has not been shown to affect the course or outcome of pregnancy in humans, although low plasma levels hav

What do the major organs of the digestive system do, What do the major orga...

What do the major organs of the digestive system do? They are salivary glands, teeth, tongue, gums, esophagus, stomach, small intestine, large intestine, pancreas, liver, and g

What is difference in electrical charge between two points, The difference ...

The difference in electrical charge between two points: Select one: is called the potential difference between those points. is called the diffusion potential between those p

What is embryonic origin of the nervous system in vertebrate, How does the ...

How does the embryo turn from gastrula into neurula? How is the neural tube formed? What is the embryonic origin of the nervous system in vertebrates? The neurula stage is divi

Explain insect resistant crops - evolutionary, Insect resistant crops (IRC)...

Insect resistant crops (IRC) Insects are a natural selection pressure so plants resistant to certain insects could have an evolutionary advantage (in natural environments)

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