CHROMOSOMAL ORGANISATION (Chroma-colour, soma-body)

• Discover by – Strasburg 1875/ Darlington/ Walther Flemming in 1882
• Name – Waldeyer 1888
• These are the genetic material which are present in nucleus
• It can be seen in Metaphase stag of cell division
• It made up of DNA and the genetic carrier gene are present on it
• These are capable to self replication.
• These are transmit genetic material form one generation to another generation by the genes, these are called genetic carrier

CHROMOSOME NUMBERS

• All animals have a characteristic number of chromosomes in their body cells called the diploid (or 2n) number. This (2N) No. is fixed in all spp
• These occur as homologous pairs, one member of each pair having been acquired from the gamete of one of the two parents of the individual whose cells are being examined.
• At the time of gametes formation, their number remain half (N), that become 2N again after fertilization.
• Eg- Onion (2N)=16 N= 8Human 2N = 46 N= 23 Zea mays 2N= 20 N=10 Tomato 2N=24 N=12 Potato 2N= 78, Wheat 2N= 42 Cotton 2N= 52 Cabbage = 2N 18  

CHROMOSOMAL ORGANISATION

Eukaryotic CHROMOSOMAL ORGANISATION

The following material are present in the Eukaryotic Chromosome

• 1 DNA
• 2 RNA
• 3 Protein (A) Histone (B) Non Histone
• 4 Ca, Fe, Mg, Zn.
• The chemical composition is different in all the stage of cell division.
• E.g.- During the Metaphase stage DNA- 15-20% RNA 10-15% and Protein 68-72% other wise during the Interphase – DNA Become increase 33-40%

1.DNA

• Chromosome are formed by the multiple coiling of DNA
• The DNA which is present in the chromosome are control the all metabolic activity and genetic activity.
• In eukaryotic cell two types of DNA are present
• 1- Normal/Unique /Non Repetitive DNA
• 2- Repetitive DNA
• This is present in alternative sequence.
• In eukaryotic cell 30-35 % DNA are unique DNA.
• In Unique DNA the Base are different to each other.
• This DNA formed Gene which is called Exon / Cistron.
• In Repetitive DNA Base sequence are repeated many time.
• It formed Heterochromatic part.
• These are called Intron

RNA

• 5% RNA is present in Chromosome
• It is called Chromosomal RNA
• It help in binding of Protein to the DNA
• It form chromatin fiber.

Protein

Two types of proteins are present in chromosome.

1- Histone protein

• It is basic protein which made up of Arginine and Lysine
• It is 80% part of the total protein
• It is present in ratio of DNA : Histone = 1:1
• It is H1, H2a, H2b, H3, and H4 types
• It is bind to the major groove of the DNA
• In this the positive end histone are bind to the negatively charged end of phosphate in DNA by electrostatic bond, it give DNA flexibility and stability. 

2- Non – Histone protein

• It is 20% part of the total protein
• It is helpful in gene regulation.
• It do Histone DNA binding with the help of RNA.

3- Ca-Mg-Zn

They made ionic bond

And help in gene regulation