Download Globins - BioQUEST

Globins
Globin diversity
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Hemoglobins (, etc)
Myoglobins (muscle)
Neuroglobins (in CNS)
Invertebrate globins
Leghemoglobins
flavohemoglobins
Addressing the breadth of
biology
Molecular biology/Biochem - protein structure,
cooperative interactions,Oxygen loading
Physiology - disease processes, specialized
Oxygen storage
Development - timing and localization of
expression
Genetics/Evolution - conservation and
diversification of sequences & functions
Introductory Analysis
Big question - What types of inferences
can we make by comparative analysis
It depends - In order to infer unobserved
properties we need to know why we
think those properties would be related.
Relationships between characters
Identity
Similarity
Homology
Relationships between characters
Identity
Similarity
Homology
binary
measured
continuous
measured
binary
inferred
Homology is relative
Are the wing of a bird and the wing of a
bat homologous structure?
Homology is relative
Are the wing of a bird and the wing of a
bat homologous structure?
YES
&
NO
Homology is relative
Are the wing of a bird and the wing of a
bat homologous structure?
YES - as forelimbs
&
NO - not as wings
Complicating Factors
• Not all similarity due to common
ancestry (homology) is equal.
• Homology is further refined into:
– Orthology (speciation)
– Paralogy (gene duplication)
– Xenology (movement between organisms)
Challenge 1
• Sketch an evolutionary tree that
includes the following 4 genes:
– Human Hb - chain
– Human Hb - chain
– Rabbit Hb - chain
– Rabbit Hb - chain
Challenge 2
• Describe the pairwise relationships
between the 4 molecules:
– Human Hb - chain
– Human Hb - chain
– Rabbit Hb - chain
– Rabbit Hb - chain
Molecules (and other features) that are
common by virtue of common ancestry
are homologous, while those that are
similar by convergence are analogous.
Among homologous molecules, those
produced by gene duplication are
paralogous and those separated by
speciation are orthologous.
Hemoglobin evolution
“Keeping oxygen under control while
using it in energy production has been
one of the great compromises struck in
the evolution of life on earth”
Hardison, 1999
Studying globins
• Deeply conserved molecule which can be
used to reconstruct species phylogenies.
• Diverse gene family that can be case study
for examining evolution in gene
structure/function relationships.
• Opportunity to look at control of expression
(timing, distribution, and amount) in gene
evolution.
• Well characterized “signatures” can be used
to search for other globins.
Complications within
development
• Even within a single species the same
molecule can assume functions in quite
different developmental pathways
• Gene duplication generates paralogous gene
families whose members can encompass an
even wider range of roles
• Domain shuffling generates molecules with
clear homology in some regions but with
potentially with quite different overall function