Chemistry of nucleic acids

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Chemistry of Nucleic Acids
R.C. Gupta M.D.
Department of Biochemistry National Institute of
Medical Sciences Jaipur, India
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Deoxyribonucleic acid (DNA)
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Miescher named it as nuclein as it was present in
the nucleus
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EMB-RCG
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Rough colony
Smooth colony
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Hydrolysis of DNA destroyed the
trans-forming activity of nuclear matter but
hydrolysis of RNA or proteins did not
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Structure of DNA
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Maurice Wilkins
Rosalind Franklin
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X-ray crystallographic images of DNA
Typical of helical structure
Typical of helical structure
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Watson
Crick
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CHARGAFFS OBSERVATIONS
Cc
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Size of purines and pyrimidines
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Watson Crick proposed a model of DNA structure
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Watson and Crick announced their discovery on Feb
28, 1953
It was published in April,1953
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5 End
3 End
3 End
5 End
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(a)
(b)
3
5
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The double helix looks like a twisted ladder
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Important features of A-, B- and Z-DNA
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Sense and anti-sense
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Replication of DNA
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The positively charged amino acids bind to
negatively charged phosphate groups of DNA
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Two molecules each of histones H2A, H2B, H3 and
H4 form an octamer around which DNA is wrapped in
two coils to form a nucleosome
Histone octamer
DNA
Nucleosome
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A nucleosome associated with histone H1 is
called a chromatosome
Histone octamer
DNA
Chromatosome
H1
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Ribonucleic acid (RNA)
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Differences between RNA and DNA
DNA RNA
Sugar Deoxyribose Ribose
Pyrimidine bases Cytosine and thymine Cytosine and uracil
Number of strands Two One
Chargaffs rule Followed Not followed
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The RNA strand may be folded upon itself
EMB-RCG
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Structure and functions of different types of RNA
Type Structure Function
mRNA Single, uncoiled strand Transmits information from DNA and serves as a template for protein synthesis
tRNA Single strand folded back on itself Brings amino acids to ribosomes for protein synthesis
rRNA Globular rRNA and proteins make up ribosomes
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Messenger RNA
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EMB-RCG
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EMB-RCG
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Transfer RNA
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5-End
3-End
Secondary structure is folded upon itself to
form an L-shaped tertiary structure
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Ribosomal RNA
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rRNA molecules are extensively folded
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EMB-RCG
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40S
60S
Ribosome
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