Molecular GeneticsDNA Structure and Organization
Sunday, November 12, 17
Brainstrom: What do we know about genetics already?
Sunday, November 12, 17
Molecular Genetics: The study of heredity
Molecular Genetics
Sunday, November 12, 17
Review: DNADNA: Deoxyribonucleic Acid
OO=P-O O
Phosphate Group
CH2
O
C1C4
C3 C2
5
Sugar(deoxyribose)
NNitrogenous base (A, G, C, or T)
Sunday, November 12, 17
DNA: Double Helix
P
P
P
O
O
O
1
23
4
5
5
3
3
5
G CP
P
PO
O
O
1
2 3
4
5
5
3
5
3
T A
Sunday, November 12, 17
DNA structureHelicalDouble StrandedStrands run antiparallel
3’ to 5’ and 5’ to 3’Phosphate starts 5’ end and the hydroxyl starts the 3’ end
Sunday, November 12, 17
Base PairsPurines (2 rings)
1)Adenine2)Guanine
Pyrimidines (1 ring)1) Cytosine2) Thymine
Sunday, November 12, 17
Base PairsPurines (2 rings)
1)Adenine2)Guanine
Pyrimidines (1 ring)1) Cytosine2) Thymine
A or G
Sunday, November 12, 17
Base PairsPurines (2 rings)
1)Adenine2)Guanine
Pyrimidines (1 ring)1) Cytosine2) Thymine
A or G
T or C
Sunday, November 12, 17
Base Pairs
Purines and Pyrimidines are held together by hydrogen bonds
2 bonds between A and T3 bonds between C and G
P
P
P
O
O
O
1
23
4
5
5
3
3
5
G CP
P
PO
O
O
1
2 34
5
5
3
5
3
T A
Sunday, November 12, 17
Base Pairs
A always binds with TC always binds with GCalled complementary base pairing
P
P
P
O
O
O
1
23
4
5
5
3
3
5
G CP
P
PO
O
O
1
2 34
5
5
3
5
3
T A
Sunday, November 12, 17
Sunday, November 12, 17
History of DNA Structure
Sunday, November 12, 17
Fredrich Miescher (1869)
Investigated pus cells, and the non-protein compound found in the nucleus
Nuclein (later named DNA)
Sunday, November 12, 17
Frederick Griffith (1928)
Studied good(S) and bad(R) bacteria
Sunday, November 12, 17
Frederick Griffith (1928)
Mice injected with heat killed S-strain mixed with living R strain somehow passed along its deadly properties
Sunday, November 12, 17
Frederick Griffith (1928)
Idea of “transforming principal” (the passing on of information from one strain to another)
Sunday, November 12, 17
Alfred Hershey and Martha Chase (1952)
Worked with bacteriophage marked with S and P
Sunday, November 12, 17
Alfred Hershey and Martha Chase (1952)
First marked protein coat with S
Material NOT passed on
Sunday, November 12, 17
Alfred Hershey and Martha Chase (1952)
Then marked DNA with P
Material IS passed on
Sunday, November 12, 17
Alfred Hershey and Martha Chase (1952)
Results finally determined that DNA was the hereditary material.
Sunday, November 12, 17
Erwin ChargaffLooked at DNA differences between species
Discovered that nucleotides were present in characteristic proportions across species
Sunday, November 12, 17
Erwin Chargaff
Chargaff’s Rule: The percent composition is the same for adenine and thymine, and the percent composition is the same for guanine as cytosine
Sunday, November 12, 17
Rosalind FranklinUsed X-ray diffraction to capture DNA on film
Determined DNA had a helical structure
Determined nitrogenous bases in the centre, sugar phosphate backbone on the outside
Sunday, November 12, 17
James Watson and Francis Crick
Constructed a 3D model of DNA
Credited with discovering double helix structure
Awarded the Nobel Prize in 1962
Sunday, November 12, 17