Introduction Flashcards
Histone proteins nucleotide substitution rates
- most changes have lethal consequences
- strong functional constraints again changing
Immunoglobins substitution rates
high
- selection favors mutations in these regions
Compare Different types of DNA evolution rates
non-synonymous - lowest - mutations change amino acid sequences synonymous/silent - codon usage bias - doesn't change amino acid sequence but not high due to codon bias Introns - some splice sites can me mutated or selected against Pseudogenes - evolve neutrally
molecular clocks
synonymous substitutions can be looked at over time to find when sequences diverged
- but not fool proof
- silent site but be neutral and silent substitution rate is not consistent
codon usage bias
certain codon preferentially used to code for aa
- varies by organism
- can select against nucleotide changes at silent sites
- not all silent sites are neutral evolving
origins of new genes
- gene duplication
- retro-position
- exon shuffling
- integration of transposable elements
- gene fusion
- gene fission
- de novo
- horizontal or lateral gene transfer
- change in subcellular localizations
Human TPA gene
evolved from ancestral exon shuffling
Mitochondrial ribosomal protein s8
gene duplication, divergence, and change of subcellular localization
- move cytosolic homolog to mito
Mitochondrial ribosomal Protein s13
Chloroplast nuclear gene is duplicated and acquires mitochondrial signaling sequence so change in subcellular localization to mitochondria
internal duplication
ex. AFGP protein (antifreeze) part of gene is duplicated many times
Jingwei gene
gene duplication
duplicate copy 2 changes to yande gene
- retro position of another gene into yande
— know is retroposed due to no introns and it has a poly a signal
selsctive sweep
one allele rises to fixation within a population due to positive selection
how to tell if selective sweep occured
reduced nucleotide diversity in surrounding regions of gene of interest
how to study function of gene
knockout in gene region
transcriptome comparisons
Why to tell if something functions as a non-coding RNA
- dn/ds ratios between groups close to 1 so neutrally evolving
- antibody again ORF’s did not yield signal
- evaluate if feasible for translation initiation in possible start codons