Chromosomes and their organization, Biology

Assignment Help:

Chromosomes   and Their Organization

During  division  phase , the duplicated  chromatin  fibres  become extremely  shortened (= condensed),  by coiling and folding ,into short think and microscopically   visible  rod like structures  of various  shapes and sizes, It  is necessary to learn about  these  structures before  dealing with  the sequential changes of mitosis. These  structures werer  observed first  by Naegeli 1842 and later by russow 1872 and Balbiani 1876  waldeyer 1888 named these,  chromosomes gr.khroma =coloured + soma =body ) because these take a  dark  stain  when treated  with basis dyes.

Karyotype :Beneden  1888 discovered   that the  chromosomal  pattern  is a specific  character .i.e.   each  species  has  its own chromosomal  complement different  from those  of all  other  species ,This  complement  of a species is called  its karyotype  .It  implies  that in all cells   membrane  of a plant or animals  species,  not only  the number  of chromosomal is the  same  but even  the  shapes  sizes,  and structure  of   the  various chromosomes  in the set are the same .The  chromosomal  number  varies from 10 to 50 in most  of the species,  The smallest  number is however two  found  in a nematode subspecies  ascaris megalocephala  univalence, and the largest  number is 1600 in  aulacantha ( a radiolarian protozoan ) To  quote a few  examples    the chromosomal  number is 46  in man  ( Homo sapiens )  32 in Hydra vulgaris. 12  in housefly (Musca domestica ) 26 in frog  (Rana pipiens )  in rabbit, (Oryctolagus  cuniculus ) 38 in cat (Felish domesticus ) 78 in dog (cains familiaris)  80 in pigeon (Columba  livia)  8 in fruitfly ( Drosophila melanogaster ) in mosquito ( Culex pipiens ) and so on.


Related Discussions:- Chromosomes and their organization

What are the implant selection errors, Implant Selection Errors There a...

Implant Selection Errors There are a plethora of commercially available implant systems and designs. Qualitative and quantitative nature of the available bone should be careful

Nervous system - cranial nerves, CRANIAL NERVES 12 pairs. Total weig...

CRANIAL NERVES 12 pairs. Total weight 12 gms. Upto amphibian 10 pairs cranial nerves are present. 1, 2, 8, - sensory. 3, 4, 6, 11, 12, motor. 5, 7, 9, 10 - mixed. 3

Transcription and processing of trna in prokaryotes , The rRNA transcriptio...

The rRNA transcription units in E. coli hold some tRNA genes which are processed and transcribed at the time of rRNA transcription. The other tRNA genes  happen  in  clusters  of

Unconventional feed resources and anti-nutritional factors, Unconventional ...

Unconventional Feed Resources and Anti-Nutritional Factors With increasing ruminant population, there is a need to identify and introduce new and lesser-known food and feed cro

Nutritional deficiency, Iron deficiency should be treated with supplemental...

Iron deficiency should be treated with supplemental iron. • Osteoporosis should be treated with calcium and vitamin D supplements. • Depending on individual factors, patien

What are the hormones secreted by the neurohypophysis, Q. What are the horm...

Q. What are the hormones secreted by the neurohypophysis? What are their respective functions? The neurohypophysis secretes the antidiuretic hormone (ADH) and oxytocin. Oxytoci

What is rationale for menu planning, What is Rationale for Menu Planning? ...

What is Rationale for Menu Planning? 'Menu', as we all know, is nothing but a list of dishes planned for preparation, and forms the very core of all activities in the food serv

Double vessel disease, Double Vessel Disease (DVD) :  Percutaneous interve...

Double Vessel Disease (DVD) :  Percutaneous intervention with stetting is usually advised for these patients. However if it is left main equivalent disease or when block is close

Can you explain embryonic sac, Q. What is embryonic sac? Which are the cell...

Q. What is embryonic sac? Which are the cells that form the embryonic sac? What are their ploidies? The embryonic sac is female gametophyte of angiosperms. The embryonic sac

Explain irradiation, Explain Irradiation The physical process of expos...

Explain Irradiation The physical process of exposing an object, system, or a material to a high radiant energy for the sterilization or preservation.

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