Evolution of mouse globin superfamily
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Transcript Evolution of mouse globin superfamily
Evolution at the Molecular Level
Outline
Evolution of genomes
Review of various types and effects of
mutations
How larger genomes evolve through
duplication and divergence
Molecular archeology based on gene
duplication, diversification, and selection
globin gene family: an example of
molecular evolution
Speculations on how the first cell
arose
The first step to life must have been a
replicator molecule
The original replicator may have been RNA
Ribozymes?
More complex cells and multicellular
organisms appeared > 2 billion years after
cellular evolution
Earliest cells
evolved into three
kingdoms of living
organisms
Archaea and
bacteria now
contain no introns
Introns late
evolutionary
elaboration
Fig. 21.3
Basic body plans of some Burgess shale organisms
Many species resulting from metazoan explosion
have disappeared
Fig. 21.4
Evolution of humans
35 mya – primates
6 mya – humans diverged from chimpanzees
Fig. 21.5
Evolution of Humans
Human and chimpanzee genomes 99%
similar
Karyotypes almost same
No significant difference in gene function
Divergence may be due to a few thousand
isolated genetic changes not yet identified
Probably regulatory sequences
DNA alterations form the basis of
genomic evolution
Mutations arise in several ways
Replacement of individual nucleotides
Deletions / Insertions: 1bp to several Mb
Single base substitutions
Missense mutations: replace one amino acid codon with
another
Nonsense mutations: replace amino acid codon with stop
codon
Splice site mutations: create or remove exon-intron
boundaries
Frameshift mutations: alter the ORF due to base
substitutions
Dynamic mutations: changes in the length of tandem repeat
elements
Effect of mutations on population
Neutral mutations are unaffected by agents
of selection
Deleterious mutations will disappear from a
population by selection against the allele
Rare mutations increase fitness
Genomes grow in size through
repeated duplications
Some
duplications result from
transposition
Other
duplications arise from
unequal crossing over
Genetic drift and mutations can turn
duplications into pseudogenes
Diversification of a duplicated gene followed
by selection can produce a new gene
Genome size
increases
through
duplication of
exons, genes,
gene families
and entire
genomes
Fig. 21.10
Basic structure of a gene
Fig. 21.11
Genes may elongate by duplication of exons to
generate tandem exons that determine tandem
functional domains
e.g., antibody molecule
Fig. 21.12a
Exon shuffling may give rise to new genes
e.g., tissue plasminogen activator (TPA)
Fig. 21.12b
Duplications of entire genes can
create multigene families
Fig. 21.13a
Unequal crossing over can expand and
contract gene numbers in multigene families
Fig. 21.13b
Fig. 21.14a
Intergenic gene conversion can increase
variation among members of a multigene
family
One gene is changed, the other is not
Concerted evolution can lead to gene
homogeneity
Fig. 21.15
Unequal crossing over
Gene conversion
Evolution of gene superfamilies
Large set of genes divisible into smaller sets,
or families
Genes in each family more closely rated to
each other than to other members of the
family
Arise by duplication and divergence
Evolution of globin superfamily
Fig. 21.16
Organisation of globin genes
Fig. 21.16
Evolution of mouse globin superfamily
Fig. 21.16
Evolution of mouse globin superfamily
Fig. 21.16