Levels of organisation of DNA explains how 2 meters long DNA is compacted into chromatin. Useful self-assessment questions are given in the slides. If you want to know the answer, you can ask in comments.

1. Organisation
of DNA
Dr. Karthikeyan Pethusamy

2. Chromatin vs chromosome vs chromatid

3. Karyotyping

4. Karyotyping, under light microscope is commonly
done by
a) R Banding
b) Q Banding
c) G Banding
d) C Banding

6. Y-chromosome is
a) Telocentric
b) Metacentric
c) Submetacentric
d) Acrocentric

7. Karyotyping of fetus is usually done from all, EXCEPT?
A. Chorionic villus sampling
B. Cordocentesis
C. Amniocentesis
D. Fetal skin

8. Level of structural organization of DNA
Level Description stabilising forces
1°
Sequence of
nucleotides in 5′ →
3′ direction
Phosphodiester bond
2°
Double helix (B-DNA,
A-DNA, and Z-DNA)
Hydrogen bond, Stacking of
bases (Hydrophobic
interaction)
3° Supercoiling of DNA DNA-protein interactions
4° Chromatin DNA-protein interactions

9. Nucleosome

10. Composition of Histone proteins

11. Packaging of DNA

13. Supercoiling

14. Most Cellular DNA Is Underwound

15. Amino terminal tail

16. Role of histone post-translational modifications

17. Chromatin Remodelling

18. Chromatin Remodelling

19. Chromatin Remodelling

20. Euchromatin Vs Heterochromatin
Euchromatin Heterochromatin
On G - Banding Lightly stained Darkly stained
Transcriptionally Active Inactive
Evolutionary
significance
Found both in
prokaryotes and
eukaryotes
only found in
eukaryotes
Epigenetic
change
associated
Histone acetylation
Histone
deacetylation
Sensitivity to
DNAse digestion
Sensitive Resistant

21. DNAse I hypersensitivity

22. DNA footprinting

23. Chromatin Immuno
Precipitation

24. Methods to detect DNA-protein interaction
• Electrophoretic mobility shift assay
• DNase footprinting assay
• Chromatin immunoprecipitation
• South-western blotting
• Yeast One-hybrid System (Y1H)
• Bacterial one-hybrid system (B1H)
• X-ray crystallography