Embed Size (px)
Citation preview
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 are composed of:–a base
–a sugar
–a phosphate
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
uracil (U)
NH
HN
O
O
cytosine (C)
NH
N
O
NH2
thymine (T)
NH
HN
O
OCH3
(DNA only) (RNA only)guanine (G)
HN
N
N
NHH2N
O
adenine (A)
N
N
N
NH
NH2
Bases
Bases found in DNA and RNA
uracil (U)
NH
HN
O
O
cytosine (C)
NH
N
O
NH2
thymine (T)
NH
HN
O
OCH3
(DNA only) (RNA only)
Purines
Pyrimidines
guanine (G)
HN
N
N
NHH2N
O
adenine (A)
N
N
N
NH
NH2
Sugars
RNA contains D-ribose DNA contains D-deoxyribose
CH2 OH
HOH
OHO
D-deoxyribose
Found in DNAFound in RNA
CH2 OH
OHOH
OHO
D-ribose
Nucleosides Nucleoside = sugar + base
A Nucleoside
adenine (A)N
N
N
NH
NH2
CH2 OH
OHOH
OHO
D-ribose
CH2
OHOH
OHO
N
N
N
N
NH2
adenosine + H2O
uracil (U)
NH
HN
O
O
(RNA only)
CH2 OH
OHOH
OHO
D-ribose
CH2
OHOH
OHO
N
HN
O
O
uridine + H2O
Nucleosides Nucleoside = sugar + base
A Nucleoside
uracil (U)
NH
HN
O
O
(RNA only)
CH2 OH
OHOH
OHO
D-ribose
CH2
OHOH
OHO
N
HN
O
O
uridine + H2O
Nucleosides Nucleoside = sugar + base
A Nucleoside
Nucleosides
Base + Sugar = Nucleoside
Adenine Adenosine Guanine Guanosine Thymine Thymidine Cytosine Cytidine Uracil Uridine
Phosphate AMP, ADP, ATP
CH2
OHOH
OO
N
N
N
N
NH2
P
O
O-
O-
adenosine monophosphateAMP
CH2
OHOH
OO
N
N
N
N
NH2
P
O
O
O-
P
O
O-
O-
adenosine diphosphateADP
adenosine triphosphateATP
P
O
O
O-
P
O
O-
O-
CH2
OHOH
OO
N
N
N
N
NH2
P
O
O
O-
Nucleotides
BASE SUGAR PO43-
adenine ribose monophosphate
Nucleotides
BASE SUGAR PO43-
adenine ribose monophosphate
NucleoSIDEugar
adenosine
Nucleotides
BASE SUGAR PO43-
adenine ribose monophosphate
NucleoTIDEhree parts
NucleoSIDEugar
adenosine
adenosine monophosphate
Nucleotides
Nucleoside + PO43- = Nucleotide
Adenosine Deoxyadenosine 5’-monophosphate(dAMP)
Cytidine Deoxycytidine 5’-monophosphate(dCMP)
Uridine (in RNA) Uridine 5’-monophosphate(UMP)
- or -- or - Thymidine (+ 2 PO4
3- ) 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» PO4
3- 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
S
P
S
P
S
P
S
P
S
P
T
G
C
A
T
Where:S = riboseP = phosphate
G,T,A,C = bases
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
S
P
S
P
S
P
S
P
S
P
T
G
C
A
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 AGCU2)DNA sugar deoxyribose RNA sugar ribose3) 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. Opening of the superstructure
2. Relaxing the higher order structure
3. Unwinding the DNA double helix
4. Primer/Primase – initiate the replication
5. DNA polymerase – enzyme that adds the nucleotides to the chain – Pairing A-T G-C
6. Ligation – Joining of Okazaki fragments and completion of the molecule
DNA Replication View animations……… http://www.youtube.com/watch?
v=4PKjF7OumYo http://www.youtube.com/watch?v=hfZ8o9D1tus http://www.youtube.com/watch?
v=Luw5_z8mIrI http://www.youtube.com/watch?
v=nIwu5MevZyg
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
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
RNA
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 DNAREPLICATION
mRNA
TRANSCRIPTION
protein !protein !
TRANSLATION
amino acidsamino acids
