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2. Structure of Chromosomes

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1. Introduction2. Discovery of Chromosomes

3. Basic structure ofChromosomes

 . gn cance o romosomes5. The DNA Strand

6. Importance of DNA7. Summary

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Introduction• Chromosomes are the chromatin

material inside the nucleus.

•

Chromosomes are so called becausethey take up certain basic dye stainsvery readily.

• “Chromos” = colour and “soma” =body

•

Chromosomes consist of Histoneproteins and DNA (deoxy-ribonucleicacid).

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Colchicine

(0.3 ml of 1 % Colchicine)

•

It is used to stop cell cycle during Metaphase.• It is used

 –   

 – To ensure attachments of spindle fibres for

correct separation.

 – Colchicine is used in chromosome

Karyotype analysis.

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Definition of Chromosome

• Chromosomes are chromatin material

thread like structure present inside thenucleus made of DNA and Histone

genetic material (genes) from one

generation to the future generation.

• Also termed as Hereditary material.

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Discovery of Chromosomes

• E.Strasburger: Observed thread like structures

during cell division.

•Balbiani: Described rod like structures in nucleus

before cell division.

• .

called stained material “Chromatin”

• Waldeyer: Coined the term “Chromosomes”

• Sutton & Boveri: Said chromosomes are physicalstructures and transmitters of 

hereditary traits

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TELOMERE: A TELOMERE is a region of 

repetitive DNA at the end of a chromosome,

which protects the end of the chromosome

from deterioration. Its name is derived fromthe Greek words telos "end" and merοs

" ".degradation of genes near the ends of 

chromosomes by allowing for the shortening

of chromosome ends, which necessarily

occurs during chromosome replication.

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CENTROMERE: A Centromere is a

region of DNA typically found near the

middle of a chromosome where two

identical sister chromatids come

closest in contact. It is involved in cell

division as the point of mitotic spindle

attachment. The sister chromatids are

attached all along their length, but

they are closest at the centromere.

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HISTONES: Histones are stronglyalkaline proteins found in eukaryotic

cell nuclei, which package and orderthe DNA into structural units callednucleosomes. The are the chief

protein components of chromatin,act as spools around which DNA

winds, and play a role in generegulation.