Transcript Introduction to Molecular Evolution

Introduction to Molecular
Evolution
Level 3 Molecular Evolution and
Bioinformatics
Jim Provan
Page and Holmes: Chapter 1
Complete genome sequences
1.83 Mbp (1995)
12 Mbp (1996)
1.66 Mbp (1996)
106.3 Mbp (2000)
3300 Mbp (2001)
Complete genome sequences
DNA sequences are valuable because they provide
the most detailed anatomy of an organism
Much of modern biology relies on unravelling
information stored in gene sequences
Importance of molecular evolution as a science:
Gene sequences represent an invaluable document of the
history of life on earth
How do we recover and interpret this information?
The tree of life – pre 1970s style!
vs.
Prokaryotes
Eukaryotes
The tree of life – post 16S rRNA style!
Green non-sulphur
Gram- bacteria
positives
Purple bacteria
Cyanobacteria
Flavobacteria
Thermotogales
Methanosarcina
Halophiles
Methanobacterium
Methanococcus
T. celer
Thermoproteus
Pyrodictium
Animals
Slime moulds
Entamoebae
Fungi
Plants
Ciliates
Flagellates
Trichomonads
Microsporidia
Diplomonads
More recent evolution
Dentist
Patient C
Patient A
Patient G
Patient B
Patient E
Patient A
Dentist
LC 2
LC 3
Patient F
LC 9
LC 35
LC 3
Patient D
Milestones in the study of molecular
evolution
Early this century, George Nuttal mixed sera and
antisera from different species to determine “blood
relationships”:
Idea was that more closely related species would exhibit
strongest cross-reactions between sera and antisera
Displayed that degree of similarity between genes reflects
strength of evolutionary relationship between tham
Despite advances in theoretical evolutionary biology
(“neo-Darwinian synthesis”), the study of molecular
evolution made little progress in the next fifty years
due to a lack of data
Milestones in the study of molecular
evolution
In 1953, James Watson
and Francis Crick
proposed the doublehelical model of the
structure of DNA
This revealed the
mechanism by which
DNA carried hereditary
information between
generations
Milestones in the study of molecular
evolution
In 1955, Fred Sanger and colleagues sequenced the
first protein, insulin:
Sequences were obtained for cattle, pigs and sheep
Three amino acid differences showed genetic variation
alongside morphological variation
Next stage was to build models of molecular evolution:
Basic models assumed that evolution was largely a stochastic
process
Also realised that with a limited number of bases and amino
acids, observed change may not represent actual change
Controversial theory that mutations occurred at regular
intervals: the “molecular clock”
Milestones in the study of molecular
evolution
Commonly held view on
human origins was that
humans were genetically
distinct from great apes
Work of Sarich & Wilson
(1967) changed this view:
Cross-reacted serum
albumin between primates
Demonstrated that human,
gorilla and chimpazee were
genetically equidistant and
distinct from orang-utan
Calibrated molecular clock
Chimpanzee
Gorilla
Orang-utan
Human
Sivapithecus
Ramapithecus
Divergence time
> 15Myr ago
Chimpanzee
Divergence time
~5Myr ago
Gorilla
Old World monkeys
~30MYr ago
Human
Orang-utan
Sivapithecus
Ramapithecus
Old World monkeys
~30MYr ago
Milestones in the study of molecular
evolution
Real “explosion” of
information on molecular
evolution since the advent
of PCR:
Nucleotide sequences have
replaced protein sequences
Can sequence DNA from
samples thousands of years
old
Major advances in
evolutionary theory
What this course will cover
Architecture and organisation of the genome
Evolution of proteins
Phylogenetics
Evolution of natural populations
Organelle genome evolution
Bioinformatics
Tools
Practical applications