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1 DNA and DNA and Replication Replication
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1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

Jan 02, 2016

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Dustin Robinson
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Page 1: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

1

DNA and DNA and ReplicationReplication

Page 2: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

2

History History of DNAof DNA

Page 3: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

3

History of DNA

• Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA

• Proteins were composed of 20 different amino acids in long polypeptide chains

Page 4: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

4

History of DNA• Chromosomes are

made of both DNA and protein

• Experiments on bacteriophage viruses by Hershey & Chase proved that DNA was the cell’s genetic material

Radioactive 32P was injected into bacteria!

Page 5: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

5

Discovery of DNA Discovery of DNA StructureStructure

• Erwin Chargraff showed the amounts of the four bases on DNA ( A,T,C,G)

• In a body or somatic cell: A = 30.3% T = 30.3% G = 19.5% C = 19.9%

Page 6: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

6

Chargaff’s RuleChargaff’s Rule• AdenineAdenine must pair with

Thymine Thymine AA - T - T• GuanineGuanine must pair with

Cytosine Cytosine GG - C - C• The bases form weak

hydrogen bonds

G CT A

Page 7: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

7

Rosalind FranklinRosalind Franklin

Rosalind Franklin took diffraction x-ray photographs of DNA crystals

Page 8: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

8

Watson and Crick•In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays

Page 9: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

9

DNA DNA StructurStructur

ee

Page 10: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

10

DNADNA•Two strands coiled called

a double helix•Sides made of a pentose

sugar Deoxyribose bonded to phosphate (PO4) groups

•Center made of nitrogen bases bonded together by weak hydrogen bonds

Page 11: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

11

DNA Double HelixDNA Double Helix

NitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)

““Rungs of ladder”Rungs of ladder”

““Legs of ladder”Legs of ladder”

Phosphate &Phosphate &Sugar BackboneSugar Backbone

Page 12: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

12

DNADNA•Stands for

Deoxyribonucleic acid•Made up of subunits

called nucleotidesnucleotides • NucleotideNucleotide made of: made of:

1. Phosphate groupPhosphate group2. 5-carbon sugar5-carbon sugar3. Nitrogenous baseNitrogenous base

Page 13: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

13

DNA NucleotideDNA Nucleotide

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)

Page 14: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

14

DNADNA

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

Page 15: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

15

Antiparallel Antiparallel StrandsStrands

• One strand of DNA goes from 5’ to 3’ (sugars)

• The other strand is opposite in direction going 3’ to 5’ (sugars)

Page 16: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

16

DNA DNA ReplicatiReplicati

onon

Page 17: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

17

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 interphaseinterphase of mitosis of mitosis

• New cells will need New cells will need identical identical DNA strandsDNA strands

Page 18: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

Three Phases of Replication

• Initiation: Unzipping DNA

• Elongation: Making new DNA strand

• Termination: Ends at telomeres (specific repeated bases) Zipping DNA back together.

Page 19: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

19

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) The “unzipping of the DNA The “unzipping of the DNA strand is carried out by an enzymestrand is carried out by an enzyme DNA helicaseDNA helicase..

• New strands grow at the forksNew strands grow at the forks

ReplicationReplicationForkFork

Parental DNA MoleculeParental DNA Molecule

3’

5’

3’

5’

Page 20: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

20

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

Page 21: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

21

DNA ReplicationDNA Replication• BeforeBefore new DNA strands can

form, there must be RNA RNA primersprimers present to start the addition of new nucleotides

• DNA polymerase can then add the new nucleotides

• The joining of RNA primers and DNA polymerase creates an Okazaki fragment. Only occurs on lagging strand

Page 22: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

Leading and Lagging Strands

• Leading strand: starts at the 3’ end of the parent DNA forming the complementary strand of 5’ to 3’

• Lagging strand: is discontinuous (patchwork for DNA); requires many RNA primers for Okazaki fragments

Page 23: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

Okazaki Fragment

23

Page 24: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

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DNA ReplicationDNA Replication• DNA polymeraseDNA polymerase can only add can only add

nucleotides to the nucleotides to the 3’ end3’ 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 5’ to 3’ direction5’ to 3’ direction

RNARNAPrimerPrimerDNA PolymeraseDNA Polymerase

NucleotideNucleotide

5’

5’ 3’

Direction of ReplicationDirection of Replication

Page 25: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

Finishing the New DNA Strands

• DNA Ligase “zips up” the lagging DNA strand– This is done by

joining the old and new strands of DNA with hydrogen bonds.

25

Page 26: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

26

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

Page 27: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

27

Replication of Replication of StrandsStrands

Replication Fork

Point of Origin

Page 28: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

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Proofreading New Proofreading New DNADNA

• 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

Page 29: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

29

Semiconservative Model Semiconservative Model of Replicationof Replication

• 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

Page 30: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

30

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

Page 31: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

31

Question:Question:

•What would be the complementary DNA strand for the following DNA sequence?

DNA 5’-CGTATG-3’DNA 5’-CGTATG-3’

Page 32: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

32

Answer:Answer:

DNA 5’-GCGTATG-3’DNA 5’-GCGTATG-3’

DNA 3’-CGCATAC-5’DNA 3’-CGCATAC-5’

Page 33: 1 DNA and Replication 2 History of DNA 3 Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins.

33

DNA by the NumbersDNA by the Numbers• Each cell has about 2

m of DNA.• The average human

has 75 trillion cells.• The average human

has enough DNA to go from the earth to the sun more than 400 times.

• DNA has a diameter of only 0.000000002 m.

The earth is 150 billion mor 93 million miles from the sun.