DNA and RNA. 2 Replication Facts DNA has to be copied before a cell dividesDNA has to be copied...
-
Upload
osborn-davidson -
Category
Documents
-
view
219 -
download
2
Transcript of DNA and RNA. 2 Replication Facts DNA has to be copied before a cell dividesDNA has to be copied...
DNA and RNA
2
Replication FactsReplication Facts
• DNA has to be copied DNA has to be copied before a cell dividesbefore a cell divides
• DNA is copied during DNA is copied during the the SS or synthesis phase or synthesis phase of of interphaseinterphase
• New cells will need New cells will need identical identical DNA strandsDNA strands
3
Synthesis Phase (S Synthesis Phase (S phase)phase)
• S phase during interphase of the cell cycle
• Nucleus of eukaryotes
Mitosis-prophase-metaphase-anaphase-telophase
G1 G2
Sphase
interphase
DNA replication takesDNA replication takesplace in the S phase.place in the S phase.
copyright cmassengale
HOW IS DNA COPIED?Image from: http://evolution.berkeley.edu/evosite/evo101/images/dna_bases.gif
The structure of DNA explains how it can be copied.
Each strand has all the info needed to construct the __________other half.
If strands are separated,_____________ rules allowyou to fill in the complementary bases.
matching
base-pairing
5
DNA ReplicationDNA Replication
• Begins atBegins at Origins of ReplicationOrigins of Replication• Two strands open forming Two strands open forming
Replication Forks (Y-shaped Replication Forks (Y-shaped region)region)
• New strands grow at the forksNew strands grow at the forks
ReplicationReplicationForkFork
Parental DNA MoleculeParental DNA Molecule
3’
5’
3’
5’copyright cmassengale
Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand DNA
polymerase
Nitrogenous bases
Replication fork
Original strand
New strand
Sites where strand separation and replication occur are called _____________replication forks
7
DNA ReplicationDNA Replication• As the 2 DNA strands open at As the 2 DNA strands open at
the origin, the origin, Replication Replication BubblesBubbles form form
• Prokaryotes (bacteria) have a single bubble
• Eukaryotic chromosomes have MANY bubbles
Bubbles Bubbles
copyright cmassengale
8
DNA ReplicationDNA Replication
• Enzyme Enzyme HelicaseHelicase unwinds and separates unwinds and separates the 2 DNA strands by the 2 DNA strands by breaking the breaking the weak weak hydrogen bondshydrogen bonds
• Single-Strand Binding Single-Strand Binding ProteinsProteins attach and keep the 2 DNA strands separated and untwisted
copyright cmassengale
9
DNA ReplicationDNA Replication• Enzyme Enzyme TopoisomeraseTopoisomerase
attaches to the 2 forks of the bubble to relieve stressrelieve stress on the DNA moleculeDNA molecule as it separatesEnzyme
DNA
Enzyme
copyright cmassengale
10
DNA ReplicationDNA Replication• BeforeBefore new DNA strands can
form, there must be RNA RNA primersprimers present to start the addition of new nucleotides
• PrimasePrimase is the enzyme that synthesizes the RNA Primer
• DNA polymerase can then add the new nucleotides
copyright cmassengale
11copyright cmassengale
12
DNA ReplicationDNA Replication• DNA polymeraseDNA polymerase can only add can only add
nucleotides to the nucleotides to the 33 ’’ end end of of the DNA the DNA
• This causes the This causes the NEWNEW strand to strand to be built in a be built in a 55 ’’ to 3 to 3’’ direction direction
RNARNAPrimerPrimerDNA PolymeraseDNA Polymerase
NucleotideNucleotide
5’
5’ 3’
Direction of ReplicationDirection of Replicationcopyright cmassengale
13
Remember HOW the Remember HOW the Carbons Are Numbered!Carbons Are Numbered!
OO=P-O O
PhosphatePhosphate GroupGroup
NNitrogenous baseNitrogenous base (A, G, C, or T)(A, G, C, or T)
CH2
O
C1C4
C3 C2
5
SugarSugar(deoxyribose)(deoxyribose)
copyright cmassengale
14
Remember the Strands are Remember the Strands are AntiparallelAntiparallel
P
P
P
O
O
O
1
23
4
5
5
3
3
5
P
P
PO
O
O
1
2 3
4
5
5
3
5
3
G C
T A
copyright cmassengale
15
Synthesis of the New DNA Synthesis of the New DNA StrandsStrands
• The The Leading StrandLeading Strand is synthesized as a single single strand strand from the point of origin toward the opening replication fork
RNARNAPrimerPrimerDNA PolymeraseDNA PolymeraseNucleotidesNucleotides
3’5’
5’
copyright cmassengale
16
Synthesis of the New DNA Synthesis of the New DNA StrandsStrands
• The The Lagging StrandLagging Strand is is synthesized discontinuouslydiscontinuously against overall direction of replication
• This strand is made in MANY short segments It is replicated from the replication fork toward the origin
RNA PrimerRNA Primer
Leading StrandLeading Strand
DNA PolymeraseDNA Polymerase
5’
5’
3’
3’
Lagging StrandLagging Strand
5’
5’
3’
3’ copyright cmassengale
17
Lagging Strand Lagging Strand SegmentsSegments
• Okazaki FragmentsOkazaki Fragments - - series of short segments on the lagging strandlagging strand
• Must be joined together by Must be joined together by an an enzymeenzyme
Lagging Strand
RNARNAPrimerPrimer
DNADNAPolymerasePolymerase
3’
3’
5’
5’
Okazaki FragmentOkazaki Fragment
copyright cmassengale
18
Joining of Okazaki FragmentsJoining of Okazaki Fragments
• The enzyme The enzyme LigaseLigase joins the joins the Okazaki fragments together Okazaki fragments together to make one strandto make one strand
Lagging Strand
Okazaki Fragment 2Okazaki Fragment 2
DNA ligaseDNA ligase
Okazaki Fragment 1Okazaki Fragment 1
5’
5’
3’
3’
copyright cmassengale
19
Replication of StrandsReplication of StrandsReplication Fork
Point of Origin
copyright cmassengale
20
Proofreading New DNAProofreading New DNA
• DNA polymerase initially DNA polymerase initially makes about makes about 1 in 10,0001 in 10,000 base base pairing errorspairing errors
• EnzymesEnzymes proofread and proofread and correct these mistakescorrect these mistakes
• The new error rate for DNA The new error rate for DNA that has been proofread is that has been proofread is 1 1 in 1 billionin 1 billion base pairing errors base pairing errors
copyright cmassengale
REPLICATION STEPS1.Enzymes “unzip” molecule by breaking_______________ that hold the strands together and unwind it.
2. _______________ joins nucleotides using original strand as template and______________for errors.
3. Copying happens in ________ directionsalong the two strands & in __________ places at once.
Hydrogen bonds
DNA polymerase
spell checks
oppositemultiple
22
Semiconservative Model of Semiconservative Model of ReplicationReplication
• Idea presented by Idea presented by Watson & CrickWatson & Crick• TheThe two strands of the parental
molecule separate, and each acts as a template for a new complementary strand
• New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA
Parental DNA
DNA Template
New DNA
copyright cmassengale
23
DNA Damage & DNA Damage & RepairRepair
• Chemicals & ultraviolet radiation damage the DNA in our body cells
• Cells must continuously repair DAMAGED DNA
• Excision repair occurs when any of over 50 repair enzymes remove damaged parts of DNA
• DNA polymerase and DNA ligase replace and bond the new nucleotides together
copyright cmassengale
24
Question:Question:
•What would be the complementary DNA strand for the following DNA sequence?
DNA 5DNA 5’’-CGTATG-3-CGTATG-3’’copyright cmassengale
25
Answer:Answer:
DNA 5DNA 5’’-CGTATG-3-CGTATG-3’’DNA 3DNA 3’’-GCATAC-5-GCATAC-5’’
copyright cmassengale
REPLICATIONANIMATION
RNA and PROTEIN SYNTHESIS
© Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
DNADNA
•DNA contains genes, sequences of nucleotide bases
•These Genes code for polypeptides (proteins)
•Proteins are used to build cells and do much of the work inside cells
28copyright cmassengale
29
Genes & ProteinsGenes & Proteins
Proteins are made of amino acids linked together by peptide bonds
20 different amino acids exist
copyright cmassengale
30
Amino Acid StructureAmino Acid Structure
copyright cmassengale
31
PolypeptidesPolypeptides
•Amino acid chains are called polypeptides
copyright cmassengale
32
DNA Begins the DNA Begins the ProcessProcess
• DNA is found inside the nucleus• Proteins, however, are made in
the cytoplasm of cells by organelles called ribosomes
• Ribosomes may be free in the cytosol or attached to the surface of rough ER
copyright cmassengale
33
Starting with DNAStarting with DNA• DNA DNA ‘‘s codes code must be must be copiedcopied
and taken to the cytosoland taken to the cytosol• In the cytoplasm, this In the cytoplasm, this code code
must be readmust be read so so amino amino acidsacids can be assembled to can be assembled to make polypeptides make polypeptides (proteins)(proteins)
• This process is called This process is called PROTEIN SYNTHESISPROTEIN SYNTHESIS
copyright cmassengale
34
Roles of RNA and DNA
•DNA is the MASTER PLAN
•RNA is the BLUEPRINT of the
Master Plancopyright cmassengale
35
RNA Differs from DNARNA Differs from DNA
• RNA has a sugar RNA has a sugar riboseribose
DNA has a sugar DNA has a sugar deoxyribosedeoxyribose
copyright cmassengale
36
Other DifferencesOther Differences
• RNA contains RNA contains the base the base uracil uracil (U(U))DNA has DNA has thymine (T)thymine (T)
• RNA molecule is RNA molecule is single-strandedsingle-strandedDNA is DNA is double-double-strandedstranded
DNAcopyright cmassengale
37
Structure of RNAStructure of RNA
copyright cmassengale
RNA- the Other Nucleic Acid
Also made of ___________
Sugar is _______ insteadof deoxyribose.
RNA is _________ stranded
Contains _________ instead of thymine.
NUCLEOTIDES
RIBOSE
SINGLE
URACIL
http://images2.clinicaltools.com/images/gene/dna_versus_rna_reversed.jpg
3 KINDS OF RNA HELP WITH INFO TRANSFER FOR PROTEIN SYNTHESIS
_________________RNA (rRNA)Combines with proteins to form
ribosomes
_________________RNA (tRNA)transfers amino acids to the ribosomes transfers amino acids to the ribosomes
where proteins are synthesizedwhere proteins are synthesized((Matches m-RNA codon to add correctamino acids during protein synthesis)
_________________RNA (mRNA)copies DNA’s code (genetic information) copies DNA’s code (genetic information)
carries code from DNA to ribosomesrRNA and t-RNA images from © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reservedmRNA image from http://wps.prenhall.com/wps/media/tmp/labeling/1140654_dyn.gif
RIBOSOMAL
TRANSFER
MESSENGER
40
Messenger RNA• Long Straight
chain of Nucleotides
• Made in the Nucleus
• Copies DNA & leaves through nuclear pores
• Contains the Nitrogen Bases A, G, C, U ( no T )
copyright cmassengale
41
Messenger RNA (mRNA)Messenger RNA (mRNA)• Carries the information for a Carries the information for a
specific proteinspecific protein• Made up of Made up of 500 to 1000 500 to 1000
nucleotides longnucleotides long• Sequence of 3 bases called Sequence of 3 bases called
codoncodon• AUGAUG – methionine or – methionine or start codonstart codon• UAA, UAG, or UGAUAA, UAG, or UGA – – stop codonsstop codons
#85
42
Ribosomal RNA (rRNA)Ribosomal RNA (rRNA)
• rRNA is a single rRNA is a single strand strand 100 to 100 to 3000 nucleotides3000 nucleotides longlong
• GlobularGlobular in shape in shape• Made inside the Made inside the
nucleusnucleus of a cell of a cell• Associates with Associates with
proteins to form proteins to form ribosomesribosomes
• Site of Site of protein protein SynthesisSynthesis
copyright cmassengale
43
The Genetic Code
• A codon designates an amino acid
• An amino acid may have more than one codon
• There are 20 amino acids, but 64 possible codons
• Some codons tell the ribosome to stop translating
copyright cmassengale
44
The Genetic Code •Use the
code by reading from the center to the outside•Example: AUG codes for Methionine
copyright cmassengale
45
Remember the Remember the Complementary BasesComplementary Bases
On DNA: A-T C-GOn RNA: A-U C-G
copyright cmassengale
46
Transfer RNA (tRNA)Transfer RNA (tRNA)• Clover-leaf shape• Single stranded molecule with
attachment site at one end for an amino acid
• Opposite end has three nucleotide bases called the anticodon
copyright cmassengale
47
Transfer RNATransfer RNAamino acidamino acid
attachment siteattachment site
U A C
anticodonanticodoncopyright cmassengale
48
Codons and Anticodons
• The 3 bases of an anticodon are complementary to the 3 bases of a codon
• Example: Codon ACU
Anticodon UGA
UGA
ACU
copyright cmassengale
Transcription Transcription and Translationand Translation
49copyright cmassengale
50
Pathway to Making a Pathway to Making a ProteinProtein
DNADNA
mRNAmRNA
tRNA (ribosomes)tRNA (ribosomes)
ProteinProteincopyright cmassengale
51
PROTEIN PROTEIN SYNTHESISSYNTHESIS
copyright cmassengale
52
Protein SynthesisProtein Synthesis The production or synthesis of
polypeptide chains (proteins) Two phases:
Transcription & Translation mRNA must be processed
before it leaves the nucleus of eukaryotic cells
copyright cmassengale
53
DNADNA RNARNA ProteinProtein
Nuclearmembrane
TranscriptionTranscription
RNA ProcessingRNA Processing
TranslationTranslation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
EukaryotEukaryotic Cellic Cell
copyright cmassengale
54
TranscriptionTranscription
• The process of copying the sequence of one strand of DNA, the template strand
• mRNA copies the template strand
• Requires the enzyme RNA Polymerase
copyright cmassengale
RNADNA
RNApolymerase
Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)
Enzyme called _____________________ separates strands, then uses one strand as a template to assemble an RNA copy.
RNA POLYMERASE
56
Template Strand
copyright cmassengale
57
Question:Question:
What would be the What would be the complementary RNA complementary RNA strand for the following strand for the following DNA sequence?DNA sequence?
DNA 5DNA 5’’--GCGTATGGCGTATG-3-3’’
copyright cmassengale
58
Answer:Answer:
•DNA 5DNA 5’’-GCGTATG-3-GCGTATG-3’’•RNA 3RNA 3’’-CGCAUAC-5-CGCAUAC-5’’
copyright cmassengale
59
TranscriptionTranscription
• During transcription, RNA polymerase binds to DNA and separates the DNA strands
• RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into RNA
copyright cmassengale
60
TranscriptionTranscription
• Promoters are regions on DNA that show where RNA Polymerase must bind to begin the Transcription of RNA
• Called the TATA box• Specific base sequences act
as signals to stop• Called the termination signal
copyright cmassengale
61
RNA PolymeraseRNA Polymerase
copyright cmassengale
How does RNA POLYMERASE know where a gene starts and
stops?
Enzyme binds to places with specific DNA sequences called _______________.
PROMOTERS tell _________________where to start.
Signals at the end of the gene code cause transcription to _____ .
PROMOTERS
http://images2.clinicaltools.com/images/gene/dna_versus_rna_reversed.jpg
RNA POLYMERASE
stop
63
mRNA ProcessingmRNA Processing
• After the DNA is transcribed into RNA, editing must be done to the nucleotide chain to make the RNA functional
• Introns, non-functional segments of DNA are snipped out of the chain
copyright cmassengale
64
mRNA EditingmRNA Editing• Exons, segments of DNA that code for proteins, are then rejoined by the
enzyme ligase• A guanine triphosphate cap is added to the 5” end of the newly copied mRNA• A poly A tail is added to the 3’ end of the RNA• The newly processed mRNA can then leave the nucleus
copyright cmassengale
65CAPTailNew Transcript
Result of TranscriptionResult of Transcription
copyright cmassengale
66
mRNA Transcript
•mRNA leaves the nucleus through its pores and goes to the ribosomes
copyright cmassengale
67
TranslationTranslation
•Translation is the process of decoding the mRNA into a polypeptide chain
•Ribosomes read mRNA three bases or 1 codon at a time and construct the proteins
copyright cmassengale
68
TranscriptionTranscription
TranslationTranslation
copyright cmassengale
69
RibosomesRibosomes
•Made of a large and small subunit
•Composed of rRNA (40%) and proteins (60%)
•Have two sites for tRNA attachment --- P and A
copyright cmassengale
70
Step 1- InitiationStep 1- Initiation
• mRNA transcript start codon AUG attaches to the small ribosomal subunit
• Small subunit attaches to large ribosomal subunitmRNA transcript
copyright cmassengale
71
RibosomesRibosomes
PSite
ASite
Largesubunit
Small subunit
mRNAmRNA
A U G C U A C U U C G
copyright cmassengale
Step 2 - Elongation• As ribosome moves, two tRNA
with their amino acids move into site A and P of the ribosome
• Peptide bonds join the amino acids
72copyright cmassengale
73
InitiationInitiation
mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa2
A U
A
1-tRNA
U A C
aa1
anticodon
hydrogenbonds codon
copyright cmassengale
74
mRNAmRNA
A U G C U A C U U C G
1-tRNA 2-tRNA
U A C G
aa1 aa2
A UA
anticodon
hydrogenbonds codon
peptide bond
3-tRNA
G A A
aa3
ElongationElongation
copyright cmassengale
75
mRNAmRNA
A U G C U A C U U C G
1-tRNA
2-tRNA
U A C
G
aa1
aa2
A UA
peptide bond
3-tRNA
G A A
aa3
Ribosomes move over one codon
(leaves)
copyright cmassengale
76
mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa1
aa2
A UA
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
copyright cmassengale
77
mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa1aa2
A U
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
(leaves)
Ribosomes move over one codoncopyright cmassengale
78
mRNAmRNA
G C U A C U U C G
aa1aa2
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
U G A
5-tRNA
aa5
copyright cmassengale
79
mRNAmRNA
G C U A C U U C G
aa1aa2
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
U G A
5-tRNA
aa5
Ribosomes move over one codoncopyright cmassengale
80
mRNAmRNA
A C A U G U
aa1
aa2
U
primaryprimarystructurestructureof a proteinof a protein
aa3
200-tRNA
aa4
U A G
aa5
C U
aa200
aa199
terminatorterminator or stopor stop codoncodon
TerminationTermination
copyright cmassengale
81
End Product –The Protein!End Product –The Protein!• The end products of protein
synthesis is a primary structure of a protein
• A sequence of amino acid bonded together by peptide bonds
aa1
aa2 aa3 aa4aa5
aa200
aa199
copyright cmassengale
82
Messenger RNA (mRNA)Messenger RNA (mRNA)
methionine glycine serine isoleucine glycine alanine stopcodon
proteinprotein
A U G G G C U C C A U C G G C G C A U A AmRNAmRNA
startcodon
Primary structure of a proteinPrimary structure of a protein
aa1 aa2 aa3 aa4 aa5 aa6
peptide bonds
codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1
copyright cmassengale
MASTER PLAN DNA stays safe in nucleus TRANSCRIPTION (DNA→ RNA)& PROCESSINGtakes place in nucleus
TRANSLATION (RNA→ proteins)takes place on ribosomes in cytoplasm
© Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
“Blueprints” of master plan are carried to building site
http://www.home-improvement-resource.com/images/architect.jpg
RNA’s require EDITING before use
Image by Riedell
WHY WASTE IT?
Why spend energy making a large RNAand then throw parts away?
May allow same gene to be used indifferent ways in different kinds of cells.
May have a role in evolution… allows small
changes in genes to have a big effect.
HOW CAN JUST 4 BASES GIVE DIRECTIONS TO MAKE 20 AMINO ACIDS?
Message is read in groups of 3 = _________
UCGCACGGU UCG-CAC-GGU
CODON
Codons represent different amino acids
Serine- Histidine- Glycine
Section 12-3
64 possible codons
Some amino acidshave more than onecodon.
START= _______
3 codons for _____
AUG
STOP
___________ on tRNA
matches up with________ on mRNA
Images modified from © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
ANTICODON
CODON
EACH tRNA carries onlyone kind of_____________amino acid
Figure 12–18 TranslationSection 12-3
Figure 12–18 Translation (continued)Section 12-3
GENES & PROTEINSProteins are the connection
betweenthe gene code in the DNA and how
thatgene is expressed.
A gene that codes for an enzyme (protein) to make a pigment can control the color of a flower.
A gene that codes for an enzyme (protein) adds carbohydrates to glycoproteins to produce your blood type.
Enzymes catalyze and regulate chemical reactions so proteins build and operate all cell components.
DNA → DNA ____________
DNA → RNA ____________
RNA→ Protein ___________
REPLICATION
TRANSCRIPTION
TRANSLATION
from to to make up
Concept MapSection 12-3
also called which functions to also called also called which functions towhich functions to
can be
from to to make up
Concept MapSection 12-3
also called which functions to also called also called which functions towhich functions to
can be
RNA
Messenger RNA Ribosomal RNA Transfer RNA
mRNA Carry instructions rRNACombine
with proteins tRNABring
amino acids toribosome
DNA Ribosome Ribosomes
Let’s Practice!
http://learn.genetics.utah.edu/content/begin/dna/transcribe/