Hoorcollege 4
multispecies conserved sequences point to the genomic elements that are under
evolutionary constraints
comparison of genomic sequences helps to find genes, elucidate gene function and trace
evolutionary relationships
molecular clocks: substitution rates per gene/genome region, depends on mutation
frequency and evolutionary constraints (higher in functionally unconstrained sequences)
positive selection -> very rapid changes in functionally important region
genomes are quickly rearranged by chromosome translocations and addition and loss of
DNA sequences
- the rate of DNA loss and addition can vary between lineages
genome evolution by gene duplication:
- whole genome duplication
- tandem repeats of individual genes
chromatin: complex of nuclear DNA and bound proteins
- histones package DNA into nucleosomes
- 4 histons together form an octamer
- chromatin is dynamic -> remodeling complexes
- ATP-dependent nucleosome sliding, exchange of H2A-H2B histones, complete
removal of histone octamers
histones are alpha helices, which bind DNA strongly via hydrogen bonds and salt linkages
nucleosomes are packaged into chromatin fibers
heterochromatin: strongly condensed chromatin ~ 10% of the genome
euchromatin: less condensed chromatin, active transcription!
heterochromatin can spread and self-propagate (epigenetic inheritance)
- chromatin remodeling complexes // histone modifications
power of fly genetics: search for enhancers and suppressors of position effect variegation to
find chromatin regulators
multispecies conserved sequences point to the genomic elements that are under
evolutionary constraints
comparison of genomic sequences helps to find genes, elucidate gene function and trace
evolutionary relationships
molecular clocks: substitution rates per gene/genome region, depends on mutation
frequency and evolutionary constraints (higher in functionally unconstrained sequences)
positive selection -> very rapid changes in functionally important region
genomes are quickly rearranged by chromosome translocations and addition and loss of
DNA sequences
- the rate of DNA loss and addition can vary between lineages
genome evolution by gene duplication:
- whole genome duplication
- tandem repeats of individual genes
chromatin: complex of nuclear DNA and bound proteins
- histones package DNA into nucleosomes
- 4 histons together form an octamer
- chromatin is dynamic -> remodeling complexes
- ATP-dependent nucleosome sliding, exchange of H2A-H2B histones, complete
removal of histone octamers
histones are alpha helices, which bind DNA strongly via hydrogen bonds and salt linkages
nucleosomes are packaged into chromatin fibers
heterochromatin: strongly condensed chromatin ~ 10% of the genome
euchromatin: less condensed chromatin, active transcription!
heterochromatin can spread and self-propagate (epigenetic inheritance)
- chromatin remodeling complexes // histone modifications
power of fly genetics: search for enhancers and suppressors of position effect variegation to
find chromatin regulators
