Download Macroevolution

Evolution of Genomes and
Developmental Mechanisms
Chapter 24
1
Comparative Genomics
•
Chimpanzee
– Humans and chimps diverged from a common ancestor
about 5 mya.
 share about 98.7% of genes
2
Origins of Genomic Differences
•
Genome changes arise in at least six ways.
– mutation of a single gene
– regions of DNA duplicate
– large chunks of chromosomes rearrange
– individual chromosomes duplicate
– whole genomes duplicate or combine to
create polyploids
– integration of foreign DNA
3
Polyploidization
•
There is growing evidence that duplication of
fewer genes in organisms has been a major
contributor to morphological diversity.
– Polyploidy can result from either genome
duplication in one species or from
hybridization of two different species.
4
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Haploid
Diploid
Polyploid
5
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Diploid: 2 x 7
Triticum monococcum (2n = 14)
AA
Diploid: 2 x 7
Triticum searsii (2n = 14)
BB
Sterile hybrid (1n = 14)
AB
Chromosome doubling
6
Lateral Gene Transfer
•
Phylogenies are built on the assumption that
genes are passed from generation to
generation (vertical gene transfer).
– Hitchhiking genes from other species lead
to phylogenetic complexity referred to as
lateral gene transfer.
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Evolution of Development
•
Genes with similar sequences in two
different species may work in different ways.
– regulatory gene may turn on different sets
of genes in different organisms
– changing time of gene expression can
also result in dramatic changes in shape
– Convergent function
 recruitment of existing regulatory
programs for new functions
8
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Development of
free-swimming
larva
Eggs
brooded
by female
Pluteus larva
(plankton)
Direct
development
into adult
Metamorphosis and
settlement to sea-floor
Egg and
sperm
released
Adult (Benthic)
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