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

What is lipid-lowering trial, Q. What is Lipid-lowering Trial? Aggressi...

Q. What is Lipid-lowering Trial? Aggressive lipid-lowering drug treatment of persons at various risk levels reduces Coronary Artery Disease morbidity and mortality rates and in

Day-neutral plants, Day-Neutral Plants  Besides SDP and LDP, those pla...

Day-Neutral Plants  Besides SDP and LDP, those plants that flower irrespective of the length of light are called day-neutral plants. For these there is no specific requirement

Of which substance are microtubules made, Of which substance are microtubul...

Of which substance are microtubules made? In which structures and cellular processes do microtubules participate? Microtubules are made of consecutive dimers of the protein tub

What are autotrophic beings? what are heterotrophic beings, What are autotr...

What are autotrophic beings? What are heterotrophic beings? The Autotrophic beings are those that can produce their own food that is that make organic material from inorganic c

Illustrate fundamental sexual life cycles, Q. What are the three fundamenta...

Q. What are the three fundamental sexual life cycles studied in Biology? Which of them corresponds to metagenesis? Which of them is the human life cycle? Sexual reproduction ma

Mollusca, General characters of mollusca

General characters of mollusca

Explain some weight loss during breastfeeding, Explain some Weight Loss dur...

Explain some Weight Loss during breastfeeding? Some women may want to return quickly to their pre-pregnancy weight. It is important to remember that some women will lose more,

Explain anterior pituitary gland secretes hormones, Explain anterior pituit...

Explain anterior pituitary gland secretes hormones The anterior pituitary gland secretes hormones that elevate  the blood glucose and therefore antagonize the action of glucose

Explain about dry heat sterilization, Q. Explain about Dry heat sterilizati...

Q. Explain about Dry heat sterilization? It is used to sterilize glass ware, forceps, scissors, scalpels, all glass syringes, swabs, some pharmaceuticals products such as liqui

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