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

Illustrate the horizons in detail, Illustrate the Horizons in detail 'O...

Illustrate the Horizons in detail 'O'  is the  organic horizon  formed from t he organic litter derived from plants and animals and fresh or partially decomposed organic materi

Explain erythema migrans, Erythema migrans Oral antibiotic therapy sho...

Erythema migrans Oral antibiotic therapy shortens the duration of the rash and generally prevents development of late sequelae. Among the 3 drugs used for this indication, onl

Functions of cholesterol, Cholesterol is a steroid.  It is very significant...

Cholesterol is a steroid.  It is very significant constituentof cell membranes in mammals, it modulates their fluidity. Cholesterol is also the precursor of steroid hormones   such

Devonian, Devonian  is the period of geologic time from 410 - 360 million y...

Devonian  is the period of geologic time from 410 - 360 million years before the present. Life on land diversified, with amphibians appearing late in this period of time. Plants we

Characteristics of female''s skeleton, CHARACTERISTICS OF FEMALE'S SKELETON...

CHARACTERISTICS OF FEMALE'S SKELETON - 1.      Skull is lighter. 2.      Shoulders are nanow. 3.      Sacrum is shorter but wider. 4.      Pelvis is wider. 5.

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

What is the meaning of chelicifore, What is the meaning of Chelicifore? ...

What is the meaning of Chelicifore? These feeding mouthparts are found on most, pycnogonads. Though the proboscis is the main feeding structure in these animals when chelicifor

Explain the elimination of dna helicase activity in a cell, Which of the fo...

Which of the following results from the elimination of DNA helicase activity in a cell? A. The melting of the DNA double helix at the site of replication initiation will fail t

Biogeochemical cycle, what are the effects of mining and farming on the pho...

what are the effects of mining and farming on the phosphorus cycle?

Micro-organisms in medicines, In terms of western medicines, over 3000 anti...

In terms of western medicines, over 3000 antibiotics - including penicillin and tetracycline - are obtained from micro-organisms. Another product of micro-organisms i.e. cyclospori

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