Detecting and sequencing DNA at the single molecule level
1. Detecting single molecules and
sequencing DNA
Rohan T. Ranasinghe
Director of Studies in Natural Sciences
@RTRanasinghe
https://www.slideshare.net/
ro26787/stoke-chemistry-
masterclass
2. The other Director of Studies in Chemistry
Available on:
iTunes (https://goo.gl/hwMEFG)
SoundCloud (https://goo.gl/s8p8Vd)
YouTube
(www.youtube.com/channel/UCWv6XjH8pzm
WMVuE_pwz1mg)
Twitter: @SteveTheChemist and
@theevanslab.
3. Solexa sequencing
• Invented in 1997 in the
chemistry department by David
Klenerman and Shankar
Balasubramanian
• Developed by a spin-out
company in Saffron Walden
4. Solexa sequencing
• Invented in 1997 in the
chemistry department by David
Klenerman and Shankar
Balasubramanian
• Developed by a spin-out
company in Saffron Walden
• Sold for £420,000,000 in 2006
5. Solexa sequencing
• Invented in 1997 in the
chemistry department by David
Klenerman and Shankar
Balasubramanian
• Developed by a spin-out
company in Saffron Walden
The latest version of the DNA sequencer they
invented
(costs about £1,000,000)
• Sold for £420,000,000 in 2006
7. Locations and timeline
1 mile
http://www.cambridge
2000.com
Old Cavendish
Laboratory
1953: Discovery of the
structure of DNA
8. Locations and timeline
1 mile
http://www.cambridge
2000.com
Old Cavendish
Laboratory
1953: Discovery of the
structure of DNA
LMB
1977: Sanger method for
sequencing invented
http://www2.mrc-lmb.cam.ac.uk
9. Locations and timeline
1 mile
http://www.cambridge
2000.com
Old Cavendish
Laboratory
1953: Discovery of the
structure of DNA
Sanger
Institute
1993: Work on Human
genome project at the
Sanger starts
Genome Research Ltd.
LMB
1977: Sanger method for
sequencing invented
http://www2.mrc-lmb.cam.ac.uk
10. Locations and timeline
1 mile
http://www.cambridge
2000.com
Old Cavendish
Laboratory
1953: Discovery of the
structure of DNA
Chemistry
department
http://www.flickr.com/
photos/shai-
bl/5584629687/sizes/
m/in/photostream/
1997: Work on Solexa method
for sequencing started
Sanger
Institute
1993: Work on Human
genome project at the
Sanger starts
Genome Research Ltd.
LMB
1977: Sanger method for
sequencing invented
http://www2.mrc-lmb.cam.ac.uk
11. Structure of DNA
http://www.themicrobiologist.com
Solved in Cambridge in 1953 by James Watson
and Francis Crick using data collected by Rosalind
Franklin and Maurice Wilkins at King’s College
London
The key to the structure was base pairing
12. Structure of DNA
http://www.themicrobiologist.com
Solved in Cambridge in 1953 by James Watson
and Francis Crick using data collected by Rosalind
Franklin and Maurice Wilkins at King’s College
London
The key to the structure was base pairing
17. DNA Sequencing
Why would you want to sequence DNA?
A genome contains the information
required to build an organism
18. DNA Sequencing
Why would you want to sequence DNA?
A genome contains the information
required to build an organism
It’s a long book...
Wikipedia
19. DNA Sequencing
Why would you want to sequence DNA?
A genome contains the information
required to build an organism
It’s a long book...
~6,000,000,000 (6 ×109)
letters in most of the
~4×1013 cells in a human
Wikipedia
20. DNA Sequencing
Why would you want to sequence DNA?
A genome contains the information
required to build an organism
It’s a long book...
~6,000,000,000 (6 ×109)
letters in most of the
~4×1013 cells in a human
Distance between base pairs
= 0.34 nm (0.34 ×10-9 m)
Wikipedia
21. DNA Sequencing
Why would you want to sequence DNA?
A genome contains the information
required to build an organism
It’s a long book...
~6,000,000,000 (6 ×109)
letters in most of the
~4×1013 cells in a human
The DNA in one of your cells would be 2 m long in the B-form structure
Distance between base pairs
= 0.34 nm (0.34 ×10-9 m)
Wikipedia
44. The human genome project
Cost: £2,000,000,000
First draft completed: 2000
‘Finished’: 2003
http://www.c-spanvideo.org/program/157909-1
Started: 1989 (in the USA)
45. The human genome project
Cost: £2,000,000,000
First draft completed: 2000
‘Finished’: 2003
http://www.c-spanvideo.org/program/157909-1
Started: 1989 (in the USA)
“Without a doubt, this is the most important,
most wondrous map ever produced by
humankind” W.J. Clinton, 26/06/2000
46. The human genome project
Cost: £2,000,000,000
First draft completed: 2000
‘Finished’: 2003
http://www.flickr.com/photos/93425126@N00/43948
34217/in/set-72157623515077498/
http://www.c-spanvideo.org/program/157909-1
Started: 1989 (in the USA)
UK effort on the Human Genome Project largely carried
out in this building in the Sanger Centre
9 Chromosomes were sequenced here (about
a third of the genome)
“Without a doubt, this is the most important,
most wondrous map ever produced by
humankind” W.J. Clinton, 26/06/2000
47. Solexa sequencing
• Cost to sequence a human
genome: around £700 (compared
to £2,000,000,000)
• Time to sequence a human
genome: less than a day
(compared to 14 years)
• Based on a microscope that can
detect single molecules
https://www.genome.gov/sequencingcosts/
Solexa’s first
sequencer
launched
Illumina
buys
Solexa
54. Looking for a needle in a haystack?
What’s so impressive about detecting a single
molecule?
55. Looking for a needle in a haystack?
How many blades of grass on a football pitch?
What’s so impressive about detecting a single
molecule?
56. Looking for a needle in a haystack?
About 200,000,000 or 2×108
How many blades of grass on a football pitch?
What’s so impressive about detecting a single
molecule?
57. How many molecules in a vial of water?
Looking for a needle in a haystack?
About 200,000,000 or 2×108
How many blades of grass on a football pitch?
What’s so impressive about detecting a single
molecule?
58. 18 mL (1 mole) of water contains Avogadro’s
number of molecules: 6.02 ×1023
How many molecules in a vial of water?
Looking for a needle in a haystack?
About 200,000,000 or 2×108
How many blades of grass on a football pitch?
What’s so impressive about detecting a single
molecule?
59. 18 mL (1 mole) of water contains Avogadro’s
number of molecules: 6.02 ×1023
How many molecules in a vial of water?
Looking for a needle in a haystack?
About 200,000,000 or 2×108
How many blades of grass on a football pitch?
So 1 mole of grass blades would cover
6.02 ×1023 ÷ 2×108 = 3 ×1015 football pitches
What’s so impressive about detecting a single
molecule?
60. 18 mL (1 mole) of water contains Avogadro’s
number of molecules: 6.02 ×1023
How many molecules in a vial of water?
Looking for a needle in a haystack?
About 200,000,000 or 2×108
How many blades of grass on a football pitch?
So 1 mole of grass blades would cover
6.02 ×1023 ÷ 2×108 = 3 ×1015 football pitches
That’s a lot of haystacks...
What’s so impressive about detecting a single
molecule?
61. 1 mole of grass blades = 3×1015 football pitches = 15×1012 km2
What’s so impressive about detecting a single
molecule?
62. 1 mole of grass blades = 3×1015 football pitches = 15×1012 km2
Surface area of Earth = 5×108 km2
(1011 football pitches!)
What’s so impressive about detecting a single
molecule?
63. 1 mole of grass blades = 3×1015 football pitches = 15×1012 km2
Surface area of Jupiter = 6×1010 km2
What’s so impressive about detecting a single
molecule?
64. 1 mole of grass blades = 3×1015 football pitches = 15×1012 km2
Surface area of the Sun
= 6×1012 km2
What’s so impressive about detecting a single
molecule?
65. 1 mole of grass blades = 3×1015 football pitches = 15×1012 km2
Surface area of the Sun
= 6×1012 km2
1 mole of grass
blades would
cover the
surface area of
about 2.5 Suns!
What’s so impressive about detecting a single
molecule?
66. 1 mole of grass blades = 3×1015 football pitches = 15×1012 km2
Surface area of the Sun
= 6×1012 km2
1 mole of grass
blades would
cover the
surface area of
about 2.5 Suns!
All images: nasa.gov
What’s so impressive about detecting a single
molecule?
69. Solexa sequencing
Solexa sequencing uses about 103 molecules to read
100 letters
About as many blades of grass as on the penalty spot
Imaging technology: Total Internal Reflection
Fluorescence (TIRF) microscopy
70. Solexa sequencing
Solexa sequencing uses about 103 molecules to read
100 letters
About as many blades of grass as on the penalty spot
Imaging technology: Total Internal Reflection
Fluorescence (TIRF) microscopy
87. Summary
The structure of DNA, discovered in 1953 has been crucial to sequencing the human genome
The first human genome was sequenced using Fred Sanger’s method, invented in 1977. The
project ran for 14 years, costing £2 billion
New methods for sequencing use single-molecule detection to dramatically accelerate the
decoding process
One approach using single molecule techniques, invented by Shankar Balasubramanian and
David Klenerman in the chemistry department in 1997 is now widely used for sequencing
worldwide
The cost of sequencing has fallen to £700 and takes less than a day
88. Summary
The structure of DNA, discovered in 1953 has been crucial to sequencing the human genome
The first human genome was sequenced using Fred Sanger’s method, invented in 1977. The
project ran for 14 years, costing £2 billion
New methods for sequencing use single-molecule detection to dramatically accelerate the
decoding process
One approach using single molecule techniques, invented by Shankar Balasubramanian and
David Klenerman in the chemistry department in 1997 is now widely used for sequencing
worldwide
The cost of sequencing has fallen to £700 and takes less than a day