MINISTRY OF DEFENCE

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  MINISTRY OF DEFENCE. Establishment Of National University In Islamabad Total position. 29 Domicile , All over Pakistan    Qualification  intermediate to bachelor positions . Project Engineer(Civil) account Officer  supervisor assistant office boy     How to apply.   Apply online through the link https://www.fgei-cg.gov.pk/nup-rec.php   Last date to apply  02 April 2023. No TA/DA Fo Interview 
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Structure of chromosomes:



Structure Of Chromosomes:

Structure of chromosome

Structurally the chromosomes consist of following parts
1. Chromatids
2.centromere or primary construction
3. Chromonema and chromomeres
4. Secondary construction or nuclear organizer
5. Telomere




1 Chromatids
Chromosomes consist of two thread like structure called chromatids.
2. Centromere or primary construction:
The chromatids are connected with each other by a small round structure called centromere (  In centromere the proteins are present which provide attachment with microtubules are called kinetochore.
The position of the centromere is specific in the chromosomes.
3:chromonema and chromonemata:
The chromatids are composed of two thin highly coiled filaments called chromonema or chromonemata. Each chromonema contains a double stranded DNA.
Both chromonema are coiled in spiral manner and they also contain swellings on their surface called chromomeres( structural subunit of chromosomes.the arrangement of chromomere structure can help in control of gene expression.)
There are several hundreds chromomeres on each chromosomes.the thin regions in between the chromomeres on each chromosomes are called interchromomeres. The position of chromomeres in the chromonema is constant is constant in each chromosome.
The outer membrane of chromosome is called pellicle and the inner part of chromosome in which chromonema are present is known as matrix.
The modern biologist do not consider the presence of peelicle,matrix and chromonema.
4: Secondary construction or nuclear Organizer:
Certain chromosomes also contain an additional part called secondary construction. It is associated with the nucleolus so it is called Nucleolus organizer(crucial for the formation of of the nucleolus l,in humans NORs are located on the short arms of the acrocentric chromosomes 13,14,15,21 and 22.during cell division NORs do not breaks).
     Stellite body: after secondary construction a small part of chromosome is called Stellite body.the chromosomes which contain stellite body are called SAT chromosomes,term is due to Sergei Navashin 1912
5. Telomere:
It is the polar part or end portion of chromosome. It does not allow the attachment of another chromosome.(found in wide range of eukaryotic to proists,if a chromosome break then without telomere they can bind).
      (3#Next post will be about types of chromosomes on the basis of centromere and position of centromere)

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