Friedrich Miescher isolated nuclein from cell nuclei in 1869. Nuclein was later called nucleic acid and shown to have acidic properties. There are two types of nucleic acids: DNA and RNA. DNA contains the genetic instructions and is found in the cell nucleus. RNA is found throughout the cell and is involved in carrying out the instructions specified by DNA. The structure of DNA was elucidated by Watson and Crick in 1953, revealing its double helix structure with two antiparallel strands bonded together via complementary nucleotide base pairing of A=T and C=G.

1. Prof. Drs. Sutarno, MSc., PhD.

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

3.  Proteins make up the cell matrix
as well as carry out all
biochemical reactions which
sustain life as we know it
 So DNA & Proteins are both
essential molecules of life

4. Two types of nucleic acid are found
 Deoxyribonucleic acid (DNA)
 Ribonucleic acid (RNA)
© 2016 Paul Billiet ODWS

5. 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
© 2016 Paul Billiet ODWS

6. DNA as genetic material: The
circumstantial evidence
1. Present in all cells and virtually restricted to the
nucleus
2. The amount of DNA in somatic cells (body cells) of
any given species is constant (like the number of
chromosomes)
3. 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
4. The mutagenic effect of UV light peaks at 253.7nm.
The peak for the absorption of UV light by DNA
© 2016 Paul Billiet ODWS

7. NUCLEIC ACID STRUCTURE
 Nucleic acids are polynucleotides
 Their building blocks are nucleotides
© 2016 Paul Billiet ODWS

8.  The carrier of genetic information
for all complex organisms.
 Long polymer consisting of 4
bases

9. NUCLEOTIDE STRUCTURE
PHOSPHATE SUGAR
Ribose or
Deoxyribose
NUCLEOTIDE
BASE
PURINES PYRIMIDINES
Adenine (A)
Guanine(G)
Cytocine (C)
Thymine (T)
Uracil (U)
© 2016 Paul Billiet ODWS

10.  • Nitrogenous bases: Adenine
Guanine
Cytosin
Thymine
uracil
 Nucleoside: Base + Sugar
 Nucleotide: Base + Sugar + Phosphate

11. Ribose is a pentose
C1
C5
C4
C3 C2
O
© 2016 Paul Billiet ODWS

12. RIBOSE DEOXYRIBOSE
CH2OH
H
OH
C
C
OH OH
C
O
H HH
C
CH2OH
H
OH
C
C
OH H
C
O
H HH
C
Spot the difference
© 2016 Paul Billiet ODWS

13. THE SUGAR-PHOSPHATE
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
© 2016 Paul Billiet ODWS

14. ADDING IN THE BASES
 The bases are attached
to the 1st Carbon
 Their order is important
It determines the genetic
information of the
molecule
P
P
P
P
P
P
G
C
C
A
T
T© 2016 Paul Billiet ODWS

15. DNA IS MADE OF
TWO STRANDS OF
POLYNUCLEOTIDE
P
P
P
P
P
P
C
G
G
T
A
A
P
P
P
P
P
P
G
C
C
A
T
T
Hydrogen bonds
© 2016 Paul Billiet ODWS

16. 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
 Thus the sister strands are complementary but not
identical
 The bases are joined by hydrogen bonds, individually
weak but collectively strong.
© 2016 Paul Billiet ODWS

17. Erwin Chargaff’s Data (1950-51)
© 2016 Paul Billiet ODWS

18. Purines & Pyrimidines
Adenine
CytosineGuanine
Thymine
© 2016 Paul Billiet ODWS

20. Watson & Crick Base pairing
© 2016 Paul Billiet ODWS

22. The Double Helix (1953)
www.chem.ucsb.edu/.../images/WatsonCrick.jpg© 2016 Paul Billiet ODWS

25. DNA molecules usually consist of two strands
arranged in the famous double helix

26.  A bonds to T
 C bonds to G

27.  each strand of DNA has a “direction”
◦ at one end, the terminal carbon atom in the
backbone is the 5’ carbon atom of the terminal
sugar
◦ at the other end, the terminal carbon atom is the
3’ carbon atom of the terminal sugar
 therefore we can talk about the 5’ and the
3’ ends of a DNA strand
 in a double helix, the strands are
antiparallel (arrows drawn from the 5’ end
to the 3’ end go in opposite directions)

28.  RNA is like DNA except:
◦ backbone is a little different
◦ usually single stranded
◦ the base uracil (U) is used in place of
thymine (T)
 a strand of RNA can be thought of as a
string composed of the four letters: A,
C, G, U