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

Class of crustacea - branchiura, Class of Crustacea - Branchiura Branc...

Class of Crustacea - Branchiura Branchiura involves only around 130 species of ectoparasitic crustaceans living mostly on the integument and gill cavities of freshwater and ma

What is the average duration of each stage in hours, A biologist examines a...

A biologist examines a series of cells and counts 140 cells in interphase, 10 cells in metaphase, 4 cells in anaphase and 7 cells in telophase. if complete cell cycle requires 24 h

Chronic bronchitis, Chronic Bronchitis Chronic Bronchitis is defined ...

Chronic Bronchitis Chronic Bronchitis is defined clinically as hypersecretion of mucus and recurrent episode of productive cough for a period of 3 months per year at least tw

Biogeochemical cycle, The cyclic exchange of nutrient material between orga...

The cyclic exchange of nutrient material between organisms and non-living  environment is called biogeochemical  cycle ,'geo means earth: ''chemical' means chemical elements, thus

Stages of aerobic respiration, Stages of Aerobic Respiration: Glycoly...

Stages of Aerobic Respiration: Glycolysis (cytoplasm) Process 2ATP used for Glucose -> Fructose 1,6 bisphosphate Fructose splits into G3P and DHAP. DHAP

Ventricular contraction, The mitral valve has an anterior and a posterior c...

The mitral valve has an anterior and a posterior cusp. The anterior cusp is larger and is attached on the upper right part of the margin of the left AV orifice. The posterior cusp

Designer meat products, D e s ign e r Meat Products Designer/healt...

D e s ign e r Meat Products Designer/health meat products low in sodium, fat, calories could be produced by incorporating fat replacers, fibers and natural antioxidants an

What is the formula is to determinate such number?, Considering the indepen...

Considering the independent segregation of all factors, how many types of gametes does a VvXXWwYyzz individual produce? What is the formula is to determinate such number? The m

Explain the process of fatty acid elongation, The process of fatty acid elo...

The process of fatty acid elongation is similar to fatty acid synthesis as it also requires both: -malonyl CoA and NADPH -malonyl CoA and NADH -Acetyl CoA and NADH

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