genome

Genome size and content doesn’t predict

Complexity

Gene content and genome size are correlated

In bacteria not eukaryotes

Genomes bloated with

Noncoding dna

Our genome is 50% “parasites” –

Transposable elements

Exact same sequence

Is recent insertion

Prokaryotes

Efficient at screening for junk and deletions

Can select for low mutation rate

Drift barrier hypothesis

• Selection is most efficient at high Ne

• There is a “barrier” to whether or not selection can act on a mutation/variant – the barrier is imposed by drift

• For species with large Ne, this barrier will be ”low” – selection can act on mutations with relatively weak effects

• For species with small Ne, this barrier is “high” – selection can only act on mutations with relatively strong effects

• Predictions include some of the data just shown

Where do new genes come from?

• What is a gene?

• De novo gene birth is rare

• Gene duplication is common

Fate of duplicate genes – most are lost

Pseudogenes

Fate of duplicate genes – repetitive function

Resistance against pesticides in plants

Fate of duplicate genes - neofunctionalization

Duplicate acquires new function

Fate of duplicate genes - subfunctionalization

Duplicate expressed at different time points

Gene family evolution

Build trees using duplicates