Molecular Biology of the Gene Chapter 10. Viruses are biological saboteurs Hijacking the genetic...
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Transcript of Molecular Biology of the Gene Chapter 10. Viruses are biological saboteurs Hijacking the genetic...
![Page 1: Molecular Biology of the Gene Chapter 10. Viruses are biological saboteurs Hijacking the genetic material of host cells in order to reproduce themselves.](https://reader035.fdocuments.us/reader035/viewer/2022062409/56649cad5503460f9496f5ff/html5/thumbnails/1.jpg)
Molecular Biology of the Gene
Chapter 10
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Viruses are biological saboteurs Hijacking the genetic
material of host cells in order to reproduce themselves
Viruses provided some of the earliest evidence That genes are made of
DNA
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Griffith Discovers Transformation
1928 Attempting to develop a vaccine he isolated
two strains of pneumonia Rough strain was harmless Smooth strain was pathogenic
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Griffith Discovers Transformation
![Page 5: Molecular Biology of the Gene Chapter 10. Viruses are biological saboteurs Hijacking the genetic material of host cells in order to reproduce themselves.](https://reader035.fdocuments.us/reader035/viewer/2022062409/56649cad5503460f9496f5ff/html5/thumbnails/5.jpg)
Transformation
The harmless R cells had been transformed by material from the dead S cells
Descendents of the transformed cells were also pathogenic
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10.1 Experiments showed that DNA is the genetic material
The Hershey-Chase experiment showed that certain viruses reprogram host cells To produce more viruses by injecting their DNA
Head
Tail
Tail fiber
DNA
300
,00
0
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Bacteriophages
Viruses that infect bacteria
Consist of protein and DNA
Inject their hereditary material into bacteria
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The Hershey-Chase experiment
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10.2 DNA and RNA are polymers of nucleotides
DNA is a nucleic acid Made of long chains of nucleotide monomers
DNA polynucleotide
A
C
T
G
T
Sugar-phosphate backbone
Phosphate group
Nitrogenous base
SugarA
C
T
G
T
Phosphategroup
O
O–
OO P CH2
H3CC
C
C
CN
C
N
H
H
O
O
C
O
O
H
C H H
H
C
H
Nitrogenous base(A, G, C, or T)
Thymine (T)
Sugar(deoxyribose)
DNA nucleotide
DNA nucleotide
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DNA has four kinds of nitrogenous bases A, T, C, and G
CC
C
CC
C
O
N
C
H
H
ONH
H3C
H H
H
H
N
N
N
H
OC
H HN
H C
N
N N
N
C
CC
C
H
H
N
N
H
C
CN
C HN
CN
H C
O
H
H
Thymine (T) Cytosine (C) Adenine (A) Guanine (G)
PurinesPyrimidines
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• RNA is also a nucleic acidBut has a slightly different
sugarAnd has U instead of T
Nitrogenous base (A, G, C, or U)
Phosphategroup
O
O–
OO P CH2
HC
C
C
C
N
C
N
H
H
O
O
C
O
O
H
C H H
OH
C
H
Uracil (U)
Sugar(ribose)
Key
Hydrogen atom
Carbon atom
Nitrogen atom
Oxygen atom
Phosphorus atom
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DNA is a double-stranded helix
James Watson and Francis Crick Worked out the three-dimensional structure of DNA,
based on work by Rosalind
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G C
T A
A T
G
G
C
C
A T
GC
T A
T A
A T
A T
G C
A T
O
O
OH
–OP
OO
–OPO
OO
P– O
– O OP
OO
O
OH
H2C
H2C
H2C
H2C
O
O
O
O
O
O
O
O
PO–
O–
O–
O–
OH
HO
O
O
O
P
P
P
O
O
O
O
O
O
O
O
T A
G C
C G
A T
CH2
CH2
CH2
CH2
Hydrogen bond
Basepair
Ribbon model Partial chemical structure Computer model
Hydrogen bonds between basesHold the strands together
Each base pairs with a complementary partnerA with T, and G with C
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DNA Replication DNA replication depends on specific base pairing
DNA replication Starts with the separation of DNA strands
Then enzymes use each strand as a template To assemble new nucleotides into complementary strands
A T
C G
G C
A T
T A
A T
C G
G C
A T
T A
A T
C G
G C
A T
T A
A T
C G
G C
A
T
A T
CG
A
C
T
A
Parental moleculeof DNA
Both parental strands serve as templates
Two identical daughtermolecules of DNA
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DNA Replication DNA replication is a complex process
Due in part to the fact that some of the helical DNA molecule must untwist
G C
A T
G C
A T
C G
AGA
CG
C
GC
G
TA
G
C
TAT
AA
TT
A
CG
CG
CG
T
AG
C
T
A
T
A
AT
T
A
TC
T
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DNA Replication DNA replication
Begins at specific sites on the double helix
Origin of replication
Two daughter DNA molecules
Parental strand
Daughter strand
Bubble
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DNA Replication
Each strand of the double helix Is oriented in the
opposite direction (antiparallel)
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DNA Replication
Using the enzyme DNA polymeraseThe cell synthesizes one daughter strand
as a continuous piece The other strand is synthesized as a series
of short piecesWhich are then connected by the enzyme
DNA ligase
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DNA Replication