information flows from dna to rna to protein the central teaching of molecular biology dna rna...
TRANSCRIPT
• Information flows from DNA to RNA to PROTEIN
The Central Teaching of Molecular Biology
DNA
RNA
PROTEINTranscription
Translation
Blue Print
Construction
1- DNA
2- Synthesis of mRNA in the nucleus 3- mRNA
NucleusCytoplasm
1-DNA
3- mRNA
2- Synthesis of mRNA in the nucleus
Transcription
Cytoplasm
mRNA4- Movement of mRNA into cytoplasm via nuclear pore
Nucleus
Ribosome
4- Movement of mRNA into cytoplasm via nuclear pore
5- Synthesis of Protein5- Synthesis of Protein
6- Polypeptide6- PolypeptideTranslation
• DNA and RNA are called Nucleic Acids.
• Nucleic Acids store information in the form of a molecular language.
• The language or code that is written into and read from Nucleic Acids is called the genetic code.
The Genetic Code & Nucleic Acids
Between 1949 and 1953, Erwin Chargaff analyzed the nucleotide base compositions of DNA molecules found in human beings and a number of other organisms as well.
Historical Moments in the Discovery of Nucleic Structure
The four nitrogenous bases in DNA are
NN
N N
H
H
NH2
H
NN
N NH
H
O
NH2
H
N
N
O
H
H3C
H
O
H
N
N
NH2
H
H
H
O
guanine (G)
adenine (A)
cytosine (C)
thymine (T)
Purine bases
Pyrimidinebases
H
What conclusions could you make from Chargaff’s Data?
A T
C G
In 1950, after analyzing the data, Erwin Chargaff reported that even though the DNA composition varied from one species to another he suggested that there was a pairing of complementary nucleotide bases (A to T and G to C) in the DNA molecule.
Historical Moments in the Discovery of Nucleic Structure
Between 1948 and 1952, Linus Pauling discovered the role hydrogen bonding
played in the complex helical structure of polypeptides and proteins. His structural discovery, called the “alpha-helix” earned him the Nobel Prize for Chemistry for his work on molecular bonding and structure, especially in proteins.
Historical Moments in the Discovery of Nucleic Structure
alpha-helix
HydrogenBonds
Polypeptide
Protein
Between 1950 and 1953, Rosalind Franklin and
Maurice Wilkins took x-ray crystallographs
(a form of microscopic photography) that showed that the
mysterious molecule DNA had a spiral shape. They were awarded Nobel Laureates for their efforts.
Historical Moments in the Discovery of Nucleic Structure
CenterVertical
Axis
Paired Bases
TwinScaffolding
SugarSpirals
In 1953, James Watson &
Francis Crick put all the pieces of “scientific data” together and unscrambled the complex chemical structure of DNA for which they also were awarded Nobel Laureates.
Historical Moments in the Discovery of Nucleic Structure
• Pairing of complementary nucleotide bases Chargaff
• Base pairs combine using hydrogen bonds Pauling
• The DNA molecule has a spiral shape Franklin & Wilkins
• The spiral is a double alpha-helix Pauling
Watson & Crick’s DNA Model
End of Introduction to the Central Dogma of Biology
Beginning of the Structure of Nucleic Acids and DNA
•A polymer is a large molecule consisting of up to millions of repeated linked molecular units that are relatively light and simple.
•Each simple molecular unit is called a monomer
T
Ds
Nucleic Acids are Polymers
P
U
RsP
DNA monomer RNA monomer
• Monomeric units are made up of an information carrying nitrogen Base
ScaffoldConnector
Ds
Rs
Base
P
• a sugar Scaffold to hold the base
• a phosphate Connector
Nucleic Acids are Polymers
• Nucleic acids (DNA and RNA) are composed of 4 different nitrogenous bases
NN
N N
H
H
NH2
H
NN
N N
H
H
O
NH2
H
N
N
O
H
H3C
H
O
H
N
N
NH2
H
H
H
OG
A
C
T
purines pyrimidines
NN
N N
H
H
NH2
H
NN
N N
H
H
O
NH2
H
N
N
O
H
H3C
H
O
H
N
N
NH2
H
H
H
OG
A
C
T
•Each have H bond donors and acceptors
purines pyrimidines
NN
N N
H
H
NH2
H
NN
N N
H
H
O
NH2
H
N
N
O
H
H3C
H
O
H
N
N
NH2
H
H
H
OG
A
C
T
•A-T base pairs form 2 H bonds & G-C base pairs form 3 H bonds
purines pyrimidines
• In RNA the base Thymine (T) is replaced by Uracil (U)
NN
N N
H
H
NH2
H
NN
N N
H
H
O
NH2
HN
N
NH2
H
H
H
OC
T
G
A
purines pyrimidines
U
In RNA the scaffold is ribose, a pentose (five carbon) sugar
H H
OH OH
OH
H
OHCH2
H
O
1’
2’
4’
H H
OH H
OH
H
OHCH2
H
O
1’
2’
4’
In DNA the scaffold is 2’-deoxyribose, a pentose (five carbon) sugar
3’3’
5’ 5’
In both DNA and RNA the base is connected to the 1’ position of the scaffolding sugar *
H H
OH H
OH
HH
O
1’
2’
4’
N
N
O
H
H3C
H
O
H
OHCH2
* (liberating water - dehydration synthesis)
5’
3’
P
In both DNA and RNA a phosphate connector is added to the 5’ position of the scaffolding sugar
H H
OH H
O
H
OHCH2
H
O
1’
2’
4’
N
N
O
H
H3C
O
H
O-
O- O
O
3’
5’
P
A nucleoside is the chemical combination of base and sugar.
H H
OH H
O
H
CH2
H
O
1’
2’
4’
N
N
O
H
H3C
O
H
O- O
O
O-
nucleoside
5’
3’
P
A nucleotide is the chemical combination of base, sugar and phosphate.
H H
OH H
O
H
CH2
H
O
1’
2’
4’
N
N
O
H
H3C
O
H
O- O
O
O-
nucleotide
5’
3’
P
The backbone of a nucleic acid is created by connecting the phosphate of this monomer to the 3’ position of another monomer’s scaffolding sugar. H H
OH H
O
H
CH2
H
O
1’
2’
4’
5’
N
N
O
H
H3C
O
H
O- O
O
O-
H H
OH H
OH
HH
O
1’
2’3’
4’
5’
“From 5’C to 3’C”3’
5’C
3’CNucleotides are added in the 5’ to 3’ direction
Phosphate connectors, Right-hand strand 3’ to 5’
Scaffolding Sugar & Base“nucleoside”
Phosphate connectors, Left-hand strand 5’ to 3’
3-D3-DDNA in
End of the Structure of Nucleic Acids and DNA
Beginning of DNA Replication
DNA: genes on chromosomes
The DNA strand opens and will add nucleotides. G to C and T to A.
5’ 3’
5’3’
One strand grows continuously, the other grows discontinuously.
Enzymes join the strands.5’ 3’
DNA Replication (inside the nucleus)
“Parental” DNA
“Parental” DNA with a replication fork
DNA Helicase
DNA Polymerase
End of DNA Replication
Beginning of RNA Replication(Transcription)
DNA produces Protein in two steps
Transcription: mRNA production
Translation: protein production
Transcription of mRNA from DNA
“Parental” DNA
Transcription ~ mRNA Synthesis
RNA Polymerase
Single stranded mRNA
RNA
DNADNA coding sequence
RNA coding sequence
GENE
INITATION of Transcription
Elongation Phase
INITATION of Transcription
Termination Phase
INITATION of Transcription
Multiple mRNA Copies
INITATION of Transcription
During Transcription mRNA code is produced from DNA.
GGG CCC TTT AAA
CCC GGG AAA UUU
To decode DNA into RNA use these base combinations A-U, T-A, G-C, C-G
Decode the DNA sequence below into mRNA ATA TAT GCG GCC GAG TCA TAA
UAU AUA CGC CGG CUC AGU AUU
What are the base code combinations?
~ Ribosomal RNA
5,080 RNA base(in 2 or 3 molecules)~ 49 embedded proteins
1,900 RNA base(in a single molecule)~ 33 embedded proteins
Eukaryotic Ribosome
rRNA
~ Transfer RNA
Anticodon mRNA Binding Site
tRNA
Amino Acid Accepting End
Beginning of Protein Synthesis(Translation)
End of mRNA Transcription
DNA produces Protein in two steps
Transcription: mRNA production
Translation: protein production
From DNA to RNA to ProteinDNA coding sequence
RNA coding sequenceA- Inside the nucleus
C- At to Ribosome
B- In the Cytosol
mRNA
GUCGUCGUCGUCGUC
Base Triplets form the Genetic Code
Original DNABase Sequence
GACGACGACGACGAC
Triplets
The “code words” in DNA and RNA are composed of three contiguous nucleotide
bases called a triplets or CODONs.
Translated mRNABase Sequence
Remember! RNA substitutes U for T
The DNA triplets which determine the mRNA codons ... code for amino acids at the ribosome... during translation.
tRNA with and amino
acid in “tow”
tRNA’s... that matches the mRNA’s “codon”.
have an “anti-codon”...
Each of the 20 essential amino acids has it’s own special tRNA’s carriers.
mRNA
tRNA
mRNA
AAA|
Phe
UUU|
Lys
GGG|
Pro
CCC|
Gly
GGG|
Pro
CCC|
Gly
UAA|
Ile
At the ribosome... an mRNA arrives... and tRNA’s begin to bring their amino acids... tRNA anti-codons match up with mRNA codons...
The tRNA’s disengage …
… and the result is a “pre-protein” polypeptide chain.
UUU AAA CCC GGG CCC GGG AUU
bonds form between the amino acids.
Translation mRNA tRNA Protein
Video
End of Protein Synthesis(Translation)
Beginning of Extra Slides concerning DNA and RNA
How is RNA different than DNA?
•Ribose Sugar•Uracil for Thymine•Single strand•not self replicating•found all over the cell
• Nucleolus - Site of ribosome production• Nucleus - location of DNA, cell organizer• Chromosomes - coiled chromatin• Chromatin - DNA and proteins not coiled• DNA - helix shaped molecule with base sequences that make up the genetic code• RNA - made by DNA, assists DNA to make proteins as a messenger (mRNA), transfer molecule (tRNA) and ribosomal RNA (rRNA).
major groove
minor groove
DNA
DNA
protein
differences between DNA and RNA
DNA RNA
• deoxyribonucleic acid • ribonucleic acid• no hydroxyl on 2’ sugar • hydroxyl on 2’ sugar
• A, C, G, T • A, C, G, U• thymine has methyl group (CH3) • uracil has a hydrogen atom at position 5
• double stranded • single stranded or double stranded
• synthesized in 5’ -> 3’ direction • synthesized in 5’ -> 3’ direction
Information content of various organisms
Organism Millions of bp (base pairs) of DNA
Human (Homo sapiens) 3000
Yeast (Saccharomyces cerevisiae) 12
Protist (Amoeba dubia) 600000
Bacterium (Mycoplasma genetalium) 0.5
other biological uses for nucleotides/nucleosides
Intracellular communication:• cyclic adenosine monophosphate (cAMP) is a common chemical
signalling molecule. Caffeine interferes with cAMP signalling
• guanosine triphosphate (GTP) and guanosine diphosphate (GDP) are used by a class of signalling proteins in the cell. The on/off switch is determined by what molecule is bound
Energy:• adenosine triphosphate (ATP) is the energy currency of the cell• energy is stored in the covalent bonds which link the three phosphates
N N
N N
CH2O
H
NH2
H
OHP
O
O O
N N
N N
H
NH2
O
NH2
O
caffeine• mimics the effect of cAMP
• a nucleoside triphosphate is the used to build up the polymer• two phosphates are liberated (pyrophosphate) when the next nucleotide is added• this chemical reaction is energetically favorable
ATP(adenosine triphosphate)
remember, for DNA, dATP is usedATP is also the energy molecule of the cell