The Molecular Basis of Inheritance

1
Chapter 16 The Molecular Basis of Inheritance
2
Is DNA the genetic material?

• Scientists knew that genes were on chromosomes
• Scientists also knew that chromosomes were made
  of DNA and proteins (remember chromatin?)
• Which one contained the genetic information?
• Proteins?
• DNA?

Two important studies 1. Griffith described
transformation 2. Hershey and Chase DNA is
the genetic material
3
Is DNA the genetic material?

• Scientists knew that genes were on chromosomes
• Scientists also knew that chromosomes were made
  of DNA and proteins (remember chromatin?)
• Which one contained the genetic information?
• Proteins?
• DNA?

Two important studies 1. Griffith described
transformation 2. Hershey and Chase DNA is
the genetic material
4
Fig. 16-2
Griffiths Experiment
5
Is DNA the genetic material?

• Scientists knew that genes were on chromosomes
• Scientists also knew that chromosomes were made
  of DNA and proteins (remember chromatin?)
• Which one contained the genetic information?
• Proteins?
• DNA?

Two important studies 1. Griffith described
transformation 2. Hershey and Chase DNA is
the genetic material
6
Fig. 16-3
Hershey and Chase
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Fig. 16-4-1
Hershey and Chase
8
Fig. 16-4-2
Hershey and Chase
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Fig. 16-4-3
Hershey and Chase
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Fig. 16-5
Nucleic Acid Structure
Phosphate
11
Nitrogenous Bases
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Purines
Pyrimidines
Uracil in RNA
12
Fig. 16-1
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Fig. 16-6
(a) Rosalind Franklin
(b) Franklins X-ray diffraction
photograph of DNA
14
Fig. 16-7
5? end
Hydrogen bond
3? end
1 nm
3.4 nm
3? end
0.34 nm
5? end
(c) Space-filling model
(b) Partial chemical structure
(a) Key features of DNA structure
15
Fig. 16-UN1
Purine purine too wide
Pyrimidine pyrimidine too narrow
Purine pyrimidine width consistent with X-ray
data
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Fig. 16-8
Base Pairing
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Fig. 16-9-1
DNA Replication
A
T
C
G
T
A
T
A
C
G
(a) Parent molecule
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Fig. 16-9-2
DNA Replication
A
T
T
A
C
G
G
C
A
T
A
T
T
T
A
A
C
C
G
G
(b) Separation of strands
(a) Parent molecule
19
Fig. 16-9-3
DNA Replication
A
A
T
T
A
T
T
A
C
C
G
G
G
C
G
C
A
T
A
A
T
A
T
T
T
T
A
T
T
A
A
A
C
C
G
C
C
G
G
G
(c) Daughter DNA molecules, each consisting of
one parental strand and one new strand
(b) Separation of strands
(a) Parent molecule
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G
C
A
T
G
C
G
C
A
T
T
A
G
C
A
T
C
G
G
C
C
G
G
C
C
C
G
A
C
A
G
T
A
T
T
G
T
T
G
T
A
A
T
A
A
A
T
C
A
T
T
A
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Fig. 16-10
First replication
Second replication
Parent cell
(a) Conservative model
(b) Semiconserva- tive model
(c) Dispersive model
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Fig. 16-12a
DNA Replication in Prokaryotes
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Fig. 16-12b
DNA Replication in Eukaryotes
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Fig. 16-13
Replication Fork
Primase
Single-strand binding proteins
3?
Topoisomerase
5?
3?
RNA primer
5?
5?
3?
Helicase
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Fig. 16-15b
Origin of replication
3?
5?
RNA primer
5?
3?
5?
DNA pol III
Parental DNA
3?
5?
5?
3?
5?
26
Fig. 16-15a
DNA is antiparallel problem!
Overview
Origin of replication
Leading strand
Lagging strand
Primer
Leading strand
Lagging strand
Overall directions of replication
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Fig. 16-16b1
3?
5?
3?
5?
Template strand
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Fig. 16-16b2
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
29
Fig. 16-16b3
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
3?
Okazaki fragment
5?
3?
1
5?
30
Fig. 16-16b4
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
3?
Okazaki fragment
5?
3?
1
5?
5?
3?
3?
2
5?
1
31
Fig. 16-16b5
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
3?
Okazaki fragment
5?
3?
1
5?
5?
3?
3?
2
5?
1
5?
3?
3?
5?
1
2
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Fig. 16-16b6
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
3?
Okazaki fragment
5?
3?
1
5?
5?
3?
3?
2
5?
1
5?
3?
3?
5?
1
2
5?
3?
3?
5?
1
2
Overall direction of replication
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Fig. 16-17
Replication the big picture (with all the
details!)
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Fig. 16-18
Nuclease
Nucleotide Excision Repair
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Fig. 16-19
Telomeres protect the DNA from damage from
shortening
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Fig. 16-21a
Chromosome Packing
Nucleosome (10 nm in diameter)
DNA double helix
(2 nm in diameter)
H1
Histone tail
Histones
DNA, the double helix
Histones
Nucleosomes, or beads on a string (10-nm fiber)
37
Fig. 16-21b
Chromatid (700 nm)
30-nm fiber
Loops
Scaffold
300-nm fiber
Replicated chromosome (1,400 nm)
30-nm fiber
Looped domains (300-nm fiber)
Metaphase chromosome