THE NUCLEIC
ACIDS

© 2007 Paul Billiet ODWS
Friedrich Miescher in 1869




isolated what he called nuclein from the nuclei of
pus cells
Nuclein was shown to have ac...
Two types of nucleic acid are
found



Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)

© 2007 Paul Billiet ODWS
The distribution of nucleic
acids in the eukaryotic cell


DNA is found in the nucleus
with small amounts in mitochondria...
DNA as genetic material: The
circumstantial evidence
1.
2.
3.

4.

Present in all cells and virtually restricted to the nu...
NUCLEIC ACID STRUCTURE



Nucleic acids are polynucleotides
Their building blocks are nucleotides

© 2007 Paul Billiet O...
NUCLEOTIDE STRUCTURE
PHOSPATE

BASE

SUGAR
Ribose or
Deoxyribose

PURINES

Adenine (A) Cytocine (C)
Guanine(G) Thymine (T)...
Ribose is a pentose
C5
O
C1

C4

C3

© 2007 Paul Billiet ODWS

C2
Spot the difference
DEOXYRIBOSE

RIBOSE
CH2OH

OH

C
H

H

H

C
OH
© 2007 Paul Billiet ODWS

CH2OH

C

O

C

H

H

OH

O

...
THE SUGARPHOSPHATE
BACKBONE




The nucleotides are all
orientated in the same direction
The phosphate group joins the 3...
P
G

ADDING IN THE BASES

P
C





The bases are attached
to the 1st Carbon
Their order is important

P
C
P

It determin...
Hydrogen bonds
P

DNA IS MADE OF
TWO STRANDS OF
POLYNUCLEOTIDE

G

C
P

P
C

G
P

P
C

G

A

T

T

A

P

P
P

P
P
P
© 2007...
DNA IS MADE OF TWO STRANDS OF
POLYNUCLEOTIDE
The sister strands of the DNA molecule run in opposite
directions (antiparall...
Erwin Chargaff’s Data (1950-51)
Wilkins & Franklin (1952): X-ray
crystallography

© Norman Collection on the History of Molecular Biology in Novato, CA
Purines & Pyrimidines

Adenine

Guanine
© 2007 Paul Billiet ODWS

Thymine

Cytosine
Watson & Crick Base pairing

© 2007 Paul Billiet ODWS
The Double Helix (1953)

© Dr Kalju Kahn USBC Chemistry and Biochemistry

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02 the nucleic_acids

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02 the nucleic_acids

  1. 1. THE NUCLEIC ACIDS © 2007 Paul Billiet ODWS
  2. 2. Friedrich Miescher in 1869   isolated what he called nuclein from the nuclei of pus cells Nuclein was shown to have acidic properties, hence it became called nucleic acid © 2007 Paul Billiet ODWS
  3. 3. Two types of nucleic acid are found   Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) © 2007 Paul Billiet ODWS
  4. 4. The distribution of nucleic acids in the eukaryotic cell  DNA is found in the nucleus with small amounts in mitochondria and chloroplasts  RNA is found throughout the cell © 2007 Paul Billiet ODWS
  5. 5. DNA as genetic material: The circumstantial evidence 1. 2. 3. 4. Present in all cells and virtually restricted to the nucleus The amount of DNA in somatic cells (body cells) of any given species is constant (like the number of chromosomes) The DNA content of gametes (sex cells) is half that of somatic cells. In cases of polyploidy (multiple sets of chromosomes) the DNA content increases by a proportional factor The mutagenic effect of UV light peaks at 253.7nm. The peak for the absorption of UV light by DNA © 2007 Paul Billiet ODWS
  6. 6. NUCLEIC ACID STRUCTURE   Nucleic acids are polynucleotides Their building blocks are nucleotides © 2007 Paul Billiet ODWS
  7. 7. NUCLEOTIDE STRUCTURE PHOSPATE BASE SUGAR Ribose or Deoxyribose PURINES Adenine (A) Cytocine (C) Guanine(G) Thymine (T) Uracil (U) NUCLEOTIDE © 2007 Paul Billiet ODWS PYRIMIDINES
  8. 8. Ribose is a pentose C5 O C1 C4 C3 © 2007 Paul Billiet ODWS C2
  9. 9. Spot the difference DEOXYRIBOSE RIBOSE CH2OH OH C H H H C OH © 2007 Paul Billiet ODWS CH2OH C O C H H OH O C H H C C C OH OH H H
  10. 10. THE SUGARPHOSPHATE BACKBONE   The nucleotides are all orientated in the same direction The phosphate group joins the 3rd Carbon of one sugar to the 5th Carbon of the next in line. P P P P P P © 2007 Paul Billiet ODWS
  11. 11. P G ADDING IN THE BASES P C   The bases are attached to the 1st Carbon Their order is important P C P It determines the genetic information of the molecule A P T P © 2007 Paul Billiet ODWS T
  12. 12. Hydrogen bonds P DNA IS MADE OF TWO STRANDS OF POLYNUCLEOTIDE G C P P C G P P C G A T T A P P P P P P © 2007 Paul Billiet ODWS T A P
  13. 13. DNA IS MADE OF TWO STRANDS OF POLYNUCLEOTIDE The sister strands of the DNA molecule run in opposite directions (antiparallel)  They are joined by the bases  Each base is paired with a specific partner: A is always paired with T G is always paired with C Purine with Pyrimidine  This the sister strands are complementary but not identical  The bases are joined by hydrogen bonds, individually weak but collectively strong © 2007 Paul Billiet ODWS 
  14. 14. Erwin Chargaff’s Data (1950-51)
  15. 15. Wilkins & Franklin (1952): X-ray crystallography © Norman Collection on the History of Molecular Biology in Novato, CA
  16. 16. Purines & Pyrimidines Adenine Guanine © 2007 Paul Billiet ODWS Thymine Cytosine
  17. 17. Watson & Crick Base pairing © 2007 Paul Billiet ODWS
  18. 18. The Double Helix (1953) © Dr Kalju Kahn USBC Chemistry and Biochemistry Public Domain image

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