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Protein Synthesis
DNA Transcription and Translation
What is the purpose for proteins? We What is the purpose for proteins? We are made of protein!are made of protein!
• antibody: fight diseases
• Muscle contractions
• Enzymes
• Hormones
• Hair, feathers, beaks, nails, horns, etc.
• Egg whites
• Transport proteins: blood(hemoglobin)
Protein StructureProtein Structure
• Made up of amino acids
• Polypeptide- string of amino acids
• ONLY 20 amino acids are arranged in different orders to make a variety of proteins!!!! Amino acids are in the cytoplasm.
• Assembled on a ribosome
How Does Our Body Create Proteins from DNA?? Its in the nucleus!!!!!!
DNA
mRNA
Transcription
Introduction
The Central Dogma of Molecular Biology
Cell
Polypeptide(protein)
TranslationRibosome
DOGMA?
This central dogma(process) was develop by Crick.
This was a hypothesis on how the code was read from DNA then used to make proteins. Scientists did not like this term for this hypothesis because it sounds like a problem!
Central Dogma of Biology
The flow of information in the cell starts at DNA,
Location????
• Prokaryotic
Cyotoplasm and ribosomes
• Eukaryotic
Nucleus and ribosomes
DNA vs. RNA(players)DNA vs. RNA(players)
• DNA • Double Helix• Deoxyribose sugar• Adenine pairs with
Thymine (A-T)• Stays in nucleus
• RNA• Single strand• Ribose sugar• Uracil replaces
Thymine!• Leaves nucleus to
do the work
DNA vs. RNA
DNA RNADeoxyribose RibsoseThymine Uracil is one of the
bases in RNA. There is
thymine no thymine. This means
A goes with U and G still goes with C.
Double Strand Single Strand
Steps to Protein Synthesis1. Transcription – process where
DNA message is changed into mRNA then out of nucleus to the ribosomes!!!
2. Translation – process when mRNA is translated into amino acid chains(protein) on the ribosomes.
Transcription???
• Purpose?
• Creating?
• WHY WHY WHY!!!!!!
How does a protein get built??
• This is where RNA becomes involved.
• DNA is too large to get out of the nuclear membrane pores.
• SO RNA has to be made to go to the ribosomes!!!
SO, HOW DOES AN AMINO ACID CHAIN GET BUILT?
RNA stands for ribonucleic acid
Stars of Translation and Transcription
1. mRNA
2. DNA
3. rRNA
4. tRNA
5. Ribsomes
6. RNA polymerase
Three types of RNA:Three types of RNA:
• 1. mRNA• “messenger” RNA• Carries code for
proteins from DNA• Carries “codon”
• 2. tRNA• “transfer” RNA
• Attaches specific Amino Acids to the protein chain by matching the mRNA codon with the anticodon.
RNA TRANSCIPTIONThere are three (3) types RNA:1. Messanger RNA – (mRNA) carries messages from the DNA in the nucleus to the ribosomes.
tRNA2. Transfer RNA – (tRNA) 20 different
kinds which are only able to bond with one (1) specific type of amino acid.
rRNA3. Ribosomal RNA – (rRNA) major
component (part) of the ribosomes
3. 3. Ribosomal Ribosomal RNA - rRNARNA - rRNA• Where Protein
synthesis occurs
How Does RNA polymerase(complex) know where to start and stop?
• Promoter site: starting and stopping point on DNA. Specific base sequences that represents a gene.
• Termination site: Place where RNA polymerase stops!!!
• REMEMBER - only a gene is being read to make mRNA not all of your DNA.
Step 1: Step 1: • RNA polymerase complex attaches to DNA
at special places that serve as the start signal(promoter sites). Only one gene!!!!!
Step 2: Step 2: • DNA splits at site of RNA polymerase.
• RNA polymerase attaches matching bases to form new RNA strand from DNA template.
• RNA polymerase keeps adding bases making the RNA strand grow…
Step 3:Step 3:• RNA polymerase leaves DNA when reaches
the termination site(stop signal).
• RNA strand is released and goes to cytoplasm.
• DNA rewinds itself into the double helix.
Results of TranscriptionResults of Transcription
• Strand of mRNA made from the DNA
FYI
RNA polymerase doesn’t check for mistakes in the code. Doesn’t cause mutations when there is a few mistakes in proteins unlike replication.
Protein Synthesis: Protein Synthesis: TranscriptionTranscription
Making mature mRNA Original mRNA transcribed
is not mature mRNA
Exons: readable segments of mRNA that will be spliced together to make mature mRNA.
Introns: are non- readable segments of mRNA that must be removed before it leaves the nucleus
Exons vs. IntronsExons vs. Introns
Once introns removed, mRNA is ready to leave the nucleus!!!!
DNA
Cytoplasm
Nucleus
Eukaryotic Transcription
ExportG AAAAAA
RNA
Transcription
Nuclear pores
G AAAAAA
RNAProcessing
mRNA
Prokaryotic Protein Synthesis
• All occurs in the cyotplasm!!!
Transcription is done…what Transcription is done…what now?now?
Now we have mature mRNA transcribed from the cell’s DNA. It is leaving the nucleus through a nuclear pore. Once in the cytoplasm, it finds a ribosome so that translation can begin.
We know how mRNA is made, but how do we “read” the code?
Translation
Translation is the process of decoding a mRNA molecule into a polypeptide chain or protein.
ALWAYS read mRNA!!!!!!
Reading FrameReading Frame
• Every 3 DNA bases pairs with 3 mRNA bases
• Every group of 3 mRNA bases encodes a single amino acid
• Codon- coding triplet of mRNA bases
Codons
• Each combination of 3 nucleotides on mRNA is called a codon or three-letter code word.
• Each codon specifies a particular amino acid that is to be placed in the polypeptide chain (protein).
Protein Synthesis: Translation
Start codons and Stop codonsStart codons and Stop codons
• For translation to begin, there is a START codon.
• AUG: is the 3 letter codon that starts the process.
• UAA, UGA, UAG: Stop codons.
SU
GA
R-P
HO
SP
HA
TE
BA
CK
BO
NE
B A
S E
S
H
PO
O
HO
O
O
CH2NH2N
NH
N
N
HOH
P
O
O
HO
O
O
CH2
NH2
N
N
N
N
H
P
O
OH
HO
O
O
CH2
NH2
N
N
N
N
O
A Codon
GuanineGuanine
AdenineAdenine
AdenineAdenine
Arginine
Protein Synthesis: Translation
Start Codon
• Start codon: codon AUG also serves as the “initiator” codon, which starts the synthesis of a protein.
Stop Codon
• STOP codon: Codon that signal the end of the protein. (UAA, UAG, & UGA
• Besides selecting the amino acid methionine, the codon AUG also serves as the “initiator” codon, which starts the synthesis of a protein
Protein Synthesis: Translation
•A three-letter code is used because there are 20 different amino acids that are used to make proteins.
•If a two-letter code were used there would not be enough codons to select all 20 amino acids.
•That is, there are 4 bases in RNA, so 42 (4x 4)=16; where as 43 (4x4x4)=64.
Translation•Therefore, there is a total of 64 codons with mRNA, 61specify a particular amino acid.
• This means there are more than one codon for each of the 20 amino acids.
Protein Synthesis: TranslationTransfer RNA (tRNA)
•Each tRNA molecule has 2 important sites of attachment.
•One site, called the anticodon, binds to the codon on the mRNA molecule.
•The other site attaches to a particular amino acid.
•During protein synthesis, the anticodon of a tRNA molecule base pairs with the appropriate mRNA codon.
tRNAtRNA
• Transfer RNA• Bound to one amino
acid on one end• Anticodon on the
other end complements mRNA codon
MethionineMet-tRNA
U*
9
262223Pu
16
12Py 10
25
20:1
G*
17:1
Pu
A20:2
1713
20G
A5051
656463
G
62
52
CPu
59
A*
C
Py
T49
39
4142
31
2928
Pu*
43127
U35
38
36
Py*
34
403047:1
47:15
46
Py47:16
4544
47
73CCA
707172
66676869
321
7654
A CU
Anticodon
Protein Synthesis: Translation
Parts of a RibosomesParts of a Ribosomes
• For translation to begin, 2 subunits of ribsosomes must unite, separate in cytoplasm – Large– Small
• Contain 3 binding sites – helps tRNA align to codon.– E– P– A
Protein Synthesis: Translation
RNA TRANSLATIONProtein Synthesis: the formation of a protein using information coded on DNA and carried out by RNA in the assembly of amino acids.
Proteins are:a. Amino acids in chains – 20 kindsb. Made of 10’s or 100’s or 1000’s of amino acidsc. Must be arranged in a specific sequence for each
type of proteind. Function & type of protein is determined by amino
acid sequencee. DNA makes RNAf. RNA constructs amino acids
Steps of TranslationSteps of Translation• 1. INITIATION:
A.The initiator(start) codon AUG binds to the first anticodon of tRNA, signaling the start of a protein.
B. Two parts of the ribosome join around the tRNA and mRNA.
• The amino acid methionine, the codon AUG also serves as the “initiator” codon, which starts the synthesis of a protein
TranslationTranslation• 2. ELONGATION: The anticodon of
another tRNA binds to the next mRNA codon, bringing the 2nd amino acid to be placed in the protein. This will continue until stop codon.
• As each anticodon & codon bind together a peptide bond forms between the two amino acids.
Protein Synthesis: TranslationProtein Synthesis: Translation
3. Termination: The protein chain continues to grow until a stop codon reaches the ribosome, which results in the release of the new protein and mRNA, completing the process of translation. The amino acids are bonded with a peptide bond to form a protein.
•Release factor causes the release of tRNA and mRNA.
Summary of Translation• Ribosome 2 parts come together.• mRNA attaches to ribosome.• AUG – start codon. • tRNA brings in making anticodon with
amino acid.• rRNA continues to read mRNA and bring
in making tRNA.*Stop codon will stop process. Peptide
bonds will form to make a protein.
tRNA FunctiontRNA Function
• Amino acids must be in the correct order for the protein to function correctly
• tRNA lines up amino acids using mRNA code
Protein Synthesis: TranslationProtein Synthesis: TranslationTransfer RNA (tRNA)
•Each tRNA molecule has 2 important sites of attachment.
•One site, called the anticodon, binds to the codon on the mRNA molecule.
•The other site attaches to a particular amino acid.
•During protein synthesis, the anticodon of a tRNA molecule base pairs with the appropriate mRNA codon.
MethionineMet-tRNAMet-tRNA
U*
9
262223Pu
16
12Py 10
25
20:1
G*
17:1
Pu
A20:2
1713
20G
A5051
656463
G
62
52
CPu
59
A*
C
Py
T49
39
4142
31
2928
Pu*
43127
U35
38
36
Py*
34
403047:1
47:15
46
Py47:16
4544
47
73CCA
707172
66676869
321
7654
A CU
Anticodon
AE
Large subunit
P
Small subunit
Translation - InitiationTranslation - Initiation
fMet
UACGAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA
3’
AE
Ribosome P
CCA
Arg
UCU
PheLeu
Met
SerGly
Polypeptide
Translation - ElongationTranslation - Elongation
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA
3’
AE
Ribosome P
PheLeu
Met
SerGly
Polypeptide
Arg
Aminoacyl tRNA
UCUCCA
Translation - ElongationTranslation - Elongation
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA
3’
AE
Ribosome P
Translation - ElongationTranslation - Elongation
Aminoacyl tRNA
CGA
Ala
CCA
Arg
UCU
PheLeu
Met
SerGly
Polypeptide
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA
3’
AE
Ribosome P
Translation - ElongationTranslation - Elongation
CCA
Arg
UCU
PheLeu
Met
SerGly
Polypeptide
CGA
Ala
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA
3’
Protein Synthesis: TranslationProtein Synthesis: Translation
The Genetic CodeThe Genetic Code
ACGATACCCTGACGAGCGTTAGCTATCGUGCUAUGGG ACUGProtein Synthesis: TranslationProtein Synthesis: Translation
ANYTHING
ACIDAMINE
Protein SynthesisProtein Synthesis
C
O
OHCN
H
HH
C
HO H
C
H
O
CN
H
HH
C
H H
C
H
O
OHCN
H
HH
C
HO H
Serine
C
H
O
OHCN
H
HH
C
H H
AlanineH
C
O
OHC
R
N
H
H
Amino Acid
H2O
3’
5’
5’
3’
Transcription And Translation Transcription And Translation In ProkaryotesIn Prokaryotes
Ribosome
Ribosome5’
mRNA
RNAPol.
Transcription vs. Translation ReviewTranscription vs. Translation Review
Transcription• Process by which
genetic information encoded in DNA is copied onto messenger RNA
• Occurs in the nucleus• DNA mRNA
Translation• Process by which
information encoded in mRNA is used to assemble a protein at a ribosome
• Occurs on a Ribosome• mRNA protein
ANYTHING
ACIDAMINE
Protein Synthesis
C
O
OHCN
H
HH
C
HO H
C
H
O
CN
H
HH
C
H H
C
H
O
OHCN
H
HH
C
HO H
Serine
C
H
O
OHCN
H
HH
C
H H
AlanineH
C
O
OHC
R
N
H
H
Amino Acid
H2O
AE
Ribosome P
CCA
Arg
UCU
PheLeu
Met
SerGly
Polypeptide
Translation - Elongation
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA
3’
Prokaryotic - Protein synthesis
• Location – cytoplasm
• At the same time.
• Eukaryotic – Protein synthesis
3’
5’
5’
3’
Transcription And Translation In Prokaryotes
Ribosome
Ribosome5’
mRNA
RNAPol.
(1961)(1961) Watson & Crick proposed… Watson & Crick proposed…• ……DNA controlled cell function by DNA controlled cell function by
serving as a template for serving as a template for PROTEINPROTEIN structure.structure.
• 3 Nucleotides = a triplet or 3 Nucleotides = a triplet or CODONCODON(which code for a specific AMINO ACID)(which code for a specific AMINO ACID)
See p.303See p.303
• AMINO ACIDSAMINO ACIDS are the building blocks are the building blocks of proteins.of proteins.
MUTATIONSChanges in DNA that affect genetic
information
Gene Mutations
• Point Mutations – changes in one nucleotides
1. Substitution – base is replaced• THE FAT CAT ATE THE RAT• THE FAT HAT ATE THE RAT
Gene Mutations2. Insertion – a base is added
• THE FAT CAT ATE THE RAT
• THE FAT HCA TAT ETH ERA T
H
Point Mutations that cause Frameshift Mutations – shifts the reading frame of the genetic message so that the protein may not be able to perform its function.
3. Deletion – delete a base THE FAT CAT ATE THE RAT TEF ATC ATA TET GER AT
Effects of Mutations
• Silent – When a base pair is substituted but the change still codes for the same amino acid in sequence. NO CHANGE!!!
Effects 0f Mutations
• Missense –Mutation that causes a changed amino acid. Usually harmful!!!
• EX: sickle cell amenia
Effects of Mutations
• Nonsense – Mutation that does not allow protein to form because of early stop codon
Sex Chromosome Abnormalities
• XYY Syndrome– Normal male traits– Often tall and thin– Associated with antisocial and behavioral
problems
Chromosome Mutations• Changes in number and structure of entire
chromosomes
• Original Chromosome ABC * DEF
• Deletion AC * DEF
• Duplication ABBC * DEF
• Inversion AED * CBF
• Translocation ABC * JKL
GHI * DEF
Significance of Mutations• Most are neutral
• Eye color• Birth marks
• Some are harmful• Sickle Cell Anemia• Down Syndrome
• Some are beneficial• Sickle Cell Anemia to Malaria• Immunity to HIV
What Causes Mutations?
• There are two ways in which DNA can become mutated:– Mutations can be inherited.
• Parent to child
– Mutations can be acquired.• Environmental damage• Mistakes when DNA is copied
Chromosome Mutations
• Down Syndrome– Chromosome 21 does
not separate correctly.– They have 47
chromosomes in stead of 46.
– Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of inteligence.
Chromosome Mutations
• Cri-du-chat– Deletion of material on 5th
chromosome– Characterized by the cat-like
cry made by cri-du-chat babies
– Varied levels of metal handicaps
Sex Chromosome Abnormalities• Klinefelter’s Syndrome
–XXY, XXYY, XXXY
–Male
–Sterility
–Small testicles
–Breast enlargement
Sex Chromosome Abnormalities• XYY Syndrome
–Normal male traits–Often tall and thin–Associated with antisocial and
behavioral problems
Sex Chromosome Mutations
• Turner’s Syndrome– X– Female– sex organs don't
mature at adolescence– sterility– short stature
Sex Chromosome Mutations
• XXX
–Trisomy X
–Female
–Little or no visible differences
–tall stature
–learning disabilities
–limited fertility
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