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

Phylogeny and evolution, While studying evolution, a student comes across a...

While studying evolution, a student comes across a cladogram that includes clades like amphibia, reptilia, aves, and mammalia. What must be the basal clade?

Define the features of cladosporium, Define the Features of Cladosporium? ...

Define the Features of Cladosporium? Identifying Features of Cladosporium: 1. Colonies are small, heaped, powdery and greenish black in colour. 2. Mycelium is septate and

Define prognosis of eating disorders, Define Prognosis of Eating Disorders?...

Define Prognosis of Eating Disorders? About 50% of the patients recover fully from anorexia nervosa and achieve normal weight, 30% improve but have a partial recovery and 20% w

Enumerate about the mycotic infections, Enumerate about the Mycotic Infecti...

Enumerate about the Mycotic Infections Invasion of the nervous system by a fungus is known as a mycotic infection. A fungus is any member of a large group of lower plants (in s

Can you explain nerves, Q. What are nerves? Axons extend all through th...

Q. What are nerves? Axons extend all through the body inside nerves. Nerves are axon-containing structures presenting many axons and covered by connective tissue. The nerves co

What is the form that produces gametes, In the metagenesis of Aurelia and O...

In the metagenesis of Aurelia and Obelia what is the form that produces gametes? What is the form that reproduces asexually? In the metagenesis of some coelenterates, like Obel

Define peri-implantitis, What is peri-implantitis? Peri-implantitis as ...

What is peri-implantitis? Peri-implantitis as defined by Meffert is the progressive loss of peri-implant bone as well as soft tissue inflammatory changes. Bacterial invasion of

Define energy and protein requirement in geriatric nutrition, Define Energy...

Define Energy and Protein requirements in geriatric nutrition? Decreased physical activity and changes in body composition and decreased basal metabolic rate affects the ma

Incompatibility - pollination and fertilization, Incompatibility - Pollinat...

Incompatibility - Pollination and Fertilization Plants growing under natural conditions have a preference for their mating partners. The stigma of the female parent receives a

What are vitamins, What are vitamins? What are the main vitamins needed by ...

What are vitamins? What are the main vitamins needed by humans? Most vitamins are coenzymes (fundamental substances for the enzyme functioning) that are not formed by the organ

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