Nucleotides, Nucleic Acids
and Heredity
Nucleic Acids
 Introduction
– Each cell has thousands of different proteins
– Proteins made up from about 20 AA
– Information for protein comes from parent
organism - “heredity”
– This information is contained in the
chromosomes in the nucleus of the cell
– Genes inside the chromosomes carry specific
information
Genes
 Genes
– Carry specific information regarding how to construct
proteins
– Lie in sequences along the chromosomes
Genes are made up of Nuceic Acids:
There are Two types of Nucelic Acids
» DNA
» RNA
– The information that tells the cell which proteins
to manufacture is carried in the molecules of
DNA
Nucleic Acids
 Components
of Nucleic Acids
– RNA or ribonucleic acid
» NOT found in chromosomes
» 6 types of RNA
» polymeric nucleotides
– DNA or deoxyribonucleic acid
» present in chromosomes
» polymeric nucleotides
Nucleic Acids
Nucleotides
–a base
–a sugar
–a phosphate
are composed of:
Bases
 Bases
found in DNA and RNA
– All basic because they are heterocyclic amines
– Uracil (U) found only in RNA
– Thymine (T) found only in DNA
 DNA
= A, G, C, T
 RNA = A, G, C, U
NH 2
N
NH 2
O
N
NH
N
adenine (A)
HN
H2N
N
NH
N
guanine (G)
NH
cytosine (C)
O
O
CH 3
HN
N
O
O
NH
HN
O
thymine (T)
NH
uracil (U)
(DNA only)
(RNA only)
Bases
 Bases
found in DNA and RNA
NH 2
N
Purines
O
N
HN
NH
N
adenine (A)
H2N
N
NH
N
guanine (G)
NH 2
Pyrimidines
NH
cytosine (C)
O
O
CH 3
HN
N
O
O
NH
HN
O
thymine (T)
NH
uracil (U)
(DNA only)
(RNA only)
Sugars
 RNA
contains D-ribose
 DNA contains D-deoxyribose
HO CH 2
O
OH
OH OH
D-ribose
Found in RNA
HO CH 2
O
OH
OH H
D-deoxyribose
Found in DNA
Nucleosides
 Nucleoside
= sugar + base
NH 2
adenine (A)
NH 2
N
N
N
NH
N
N
N
D-ribose
HO CH 2
O
OH
OH
OH
N
adenosine
HO CH 2
O
OH
OH
A Nucleoside
+ H2 O
Nucleosides
 Nucleoside
= sugar + base
O
uracil (U)
(RNA only)
O
HN
O
NH
HN
O
D-ribose
HO CH 2
O
OH
OH
OH
N
HO CH 2
O
uridine
OH OH
A Nucleoside
+ H2O
Nucleosides
 Nucleoside
= sugar + base
O
uracil (U)
(RNA only)
O
HN
O
NH
HN
O
D-ribose
HO CH 2
O
OH
OH
OH
N
HO CH 2
O
uridine
OH OH
A Nucleoside
+ H2O
Nucleosides
Base
 Adenine
 Guanine
 Thymine
 Cytosine
 Uracil
+ Sugar =
Nucleoside
Adenosine
Guanosine
Thymidine
Cytidine
Uridine
Phosphate
 AMP,
ADP, ATP
NH 2
NH 2
N
N
O
O- P O CH 2
O-
N
N
O
OOH
adenosine monophosphate
AMP
O-
O
O
OH OH
adenosine diphosphate
ADP
N
N
N
N
O- P O P O CH 2
O
OH
N
N
O
NH 2
O
O
O- P O P O P O CH 2
O-
O-
O-
N
N
O
OH OH
adenosine triphosphate
ATP
Nucleotides

adenine
ribose
monophosphate
BASE
SUGAR
PO43-
Nucleotides

adenine
ribose
monophosphate
BASE
SUGAR
PO43-
adenosine
NucleoSIDE
Nucleotides

adenine
ribose
monophosphate
BASE
SUGAR
PO43-
adenosine
NucleoSIDE
adenosine monophosphate
NucleoTIDE
Nucleotides
Nucleoside + PO43- = Nucleotide
 Adenosine
Deoxyadenosine 5’-monophosphate
(dAMP)
 Cytidine
 Uridine (in RNA)
Deoxycytidine 5’-monophosphate
(dCMP)
Uridine 5’-monophosphate
(UMP)
- or -
 Thymidine (+ 2 PO43- )
Deoxythymidine 5’-diphosphate
(dTDP)
 Guanosine (+ 3 PO43- ) Deoxyguanosine 5’-triphosphate
(dGTP)
DNA - Primary Structure
 The
primary structure is based on the
sequence of nuclotides
– 1) The Backbone is made from Ribose (sugar)
and Phosphate
» PO43- connected at Ribose 3’ and 5’
– 2) The Bases (AGTC, AGUC) are side-chains
and are what makes each monomer unit different.
» Bases connected at Ribose 1’
DNA - Primary Structure
DNA - Primary Structure
DNA - Primary Structure

DNA - Primary Structure

Where:
P
S = ribose
P = phosphate
G,T,A,C = bases
G
S
P
T
S
P
A
S
P
C
S
P
S
T
DNA - Primary Structure
 The
order of the bases (-ATTGAC-)
provides the primary structure of DNA.
 The backbone of both DNA and RNA
consists of alternating sugar and phosphate
groups
– there is a 3’ end and a 5’ end
– the backbone adds stability to the structure
DNA - Primary Structure

Erwin Chargaff (1905-
)
DNA always had ratios constant:
moles adenine = moles thymine
moles guanine = moles cytosine
 Base
Pairing of:
– A-T or T-A
– G-C or C-G
P
G
S
P
T
S
P
A
S
P
C
S
P
S
T
How we Depict DNA
How we Depict DNA
DNA – Secondary Structure
 James
Watson (1928- ) and
Francis Crick (1916-2004 )
 Established 3-D structure of DNA
 Bases on adjacent strands PAIRED so that
Hydrogen bonds formed:
Complementary Base Pairing
DNA - Secondary Structure
Complementary
Base Pairing
– Adenine pairs with Thymine
– Position of H bonds and distance match
DNA - Secondary Structure
Complementary
Base Pairing
– Guanine pairs with Cytosine
– Position of H bonds and distance match
DNA - Secondary Structure
Complementary
Base Pairing
DNA - Secondary Structure
DNA structure led to
explanation of the
transmission of heredity
DNA vs. RNA
 DNA
and RNA differences:
1) DNA 4 bases
AGCT
RNA 4 bases
AGCU
2)DNA sugar
deoxyribose
RNA sugar
ribose
3) DNA is almost always double stranded
RNA is single stranded
A pairs with U (not T)
DNA Replication
Each
gene is a section of DNA
– 1000-2000 base sequences
– Each gene codes for 1 protein molecule
– Each cell contains ALL of the info for the
organism
– Replication is the process of copying all genetic
information on the DNA to new DNA
DNA Replication Steps
1.
2.
3.
4.
5.
6.
Opening of the superstructure
Relaxing the higher order structure
Unwinding the DNA double helix
Primer/Primase – initiate the replication
DNA polymerase – enzyme that adds the
nucleotides to the chain – Pairing A-T G-C
Ligation – Joining of Okazaki fragments and
completion of the molecule
DNA Replication
 View
animations………
 http://www.youtube.com/watch?v=4PKjF7
OumYo
 http://www.youtube.com/watch?v=hfZ8o9
D1tus
 http://www.youtube.com/watch?v=Luw5_z
8mIrI
 http://www.youtube.com/watch?v=nIwu5M
evZyg
DNA Replication
Semiconservative
Replication
– The result is 4 strands of DNA
– Only half of each helix is “new”
– Semiconservative since one half of each
new helix is a daughter strand and half a
parent
DNA Replication

DNA Replication

DNA Replication
Okazaki fragments
DNA Replication

Okazaki fragments
Types of RNA
mRNA
- Messenger RNA
tRNA
- Transfer RNA
rRNA
- Ribosomal RNA
snRNA
– Small nuclear RNA
miRNA – Micro RNA
siRNA – Small interfering RNA
(1933)
mRNA
 Messenger
RNA
 Carries info from DNA to cytoplasm
 Not stable (not long lasting)
 Info is for single protein synthesis
 Exactly complementary to one DNA
strand
tRNA
 Transfer
RNA (tRNA)
 Transfers amino acids to the point of
protein synthesis
 Small (73-93 nucleotides)
 About 20 exist (one for each AA!)
 “L-shaped”
 Contain some “other” modified Nucleic
Acids
Transfer RNA
rRNA
 Ribosomal
RNA (rRNA)
 Found in ribosomes
 35% protein, 65% rRNA make up
ribosomes
 Large molecules with MW=1,000,000
 Protein synthesis takes place on
ribosomes
RNA
snRNA
– Small nuclear RNA
– Helps with the processing of the mRNA
transcribed from DNA
miRNA
– Micro RNA
– Important in the timing of organism
development
siRNA
– Small interfering RNA
– Help control Gene expression
Transmission of Information
Step
1 - Transcription
– Copying the “code” from DNA to to mRNA
– The mRNA then moves to the ribosome
Step
2 - Translation
– Deciphering the “code” from mRNA into protein
– Each 3 nucleotides code for a specific AA
 Next
Chapter Discussion!!!!!!!!!!
Transmission of Information
SUMMARY
DNA
REPLICATION
DNA
TRANSCRIPTION
mRNA
TRANSLATION
amino acids
protein !