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 poor growth - clinical signs of kwashiorkor, Explain Poor growth - ...

Explain Poor growth - clinical signs of kwashiorkor? Growth retardation is the earliest manifestation of kwashiorkor, the child will be lighter and shorter than its normal peer

What is phylum annelida - segmented worms, What is Phylum Annelida - Segmen...

What is Phylum Annelida - Segmented Worms? Members of this Phylum are commonly known as the segmented worms. The body of a segmented worm is made of many individual ring-like s

Cardio pulmonary resuscitation, CARDIO PULMONARY RESUSCITATION: Cessat...

CARDIO PULMONARY RESUSCITATION: Cessation of cardiac activity is determined by  inability to palpate a central pulse,  unresponsiveness and Gnea. CPR consists of  measures for

Amitosis, AMITOSIS This  is  direct  cell division  in which  the genet...

AMITOSIS This  is  direct  cell division  in which  the genetic material is not duplicated and  hence its distribution  to the daughter cells  is not  precisely half  and half,

Photosynthesis, test to prove that carbondioxide is needed for photosynthes...

test to prove that carbondioxide is needed for photosynthesis to take place

Explain zanamivir, Zanamivir  (Relenza) Started within 2 days after on...

Zanamivir  (Relenza) Started within 2 days after onset of symptoms, this orally inhaled neuraminidase inhibitor can shorten the duration of illness and may decrease the incide

Sulphur cycle, Sulphur is one of important of proteins vitamins and hormone...

Sulphur is one of important of proteins vitamins and hormones. It plays a very crucial role in health of both plants and animals. Most of earth sulphur is tied up in rocks and salt

Is neuron a synapses onto neuron b, Is Neuron A synapses onto Neuron B ...

Is Neuron A synapses onto Neuron B Consider Neuron B in the frog central nervous system whose plasma membrane has a newly discovered ligand-gated ionotropic receptor, named the

What are the major factors of colloidal dispersion, What are the major fact...

What are the major factors of colloidal dispersion The adsorption of ions by colloidal particles is a major factor in stabilizing a colloidal dispersion, since the colloidal pa

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