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

Why alkaline phosphatases use water as a second substrate, Alkaline Phospha...

Alkaline Phosphatases use water as a second substrate. Why do we still treat their kinetics as if they were for a single-substrate reaction?

Define the sarcoplasmic reticulum membranes, An increase in the calcium con...

An increase in the calcium conductance of all sarcoplasmic reticulum membranes of a skeletal muscle with no external forces on it leads to A. increased binding of calcium ions

Is there interphase again between meiosis i and meiosis ii, Is there interp...

Is there interphase again between meiosis I and meiosis II? There is no interphase nor DNA duplication among the divisions of meiosis. Only a short interval called diakinesis h

Slim mold, what is the cycle of slime moldand thier structure

what is the cycle of slime moldand thier structure

What is the type of meiosis that occurs in pteridophytes, How are gametes f...

How are gametes formed in the pteridophyte life cycle, by mitosis or meiosis? What is the type of meiosis that occurs in pteridophytes? In pteridophytes gametes are made by mit

Define role of leptin in controlling gene expression, Define role of Leptin...

Define role of Leptin in controlling gene expression? Leptin is a protein product (containing 167 amino acids) of the ob gene expressed exclusively in the adipose tissue. This

#title, IN WHAT ASPECT ARE CNIDARIANS SIMILAR TO PROTOZOANS

IN WHAT ASPECT ARE CNIDARIANS SIMILAR TO PROTOZOANS

Adaptation, Adaptation Closely related to irritability is the capacit...

Adaptation Closely related to irritability is the capacity of living things for adaptation. You might have noticed that whenever you go outside in the bright sun after having

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