Is there a correlation between C value and “complexity?”
no
What reason supports the idea that more genes are needed for greater organismal complexity?
plants and animals independently increase genome sizes - suggest more cell types needs more genes
Is there a correlation of coding DNA amount and organismal complexity?
weak correlation: 80-95% of genome is protein coding in prokaryotes & viruses vs. only 2-10% in verts and land plants. 10,000 fold range of genome sizes across species but only 100 fold range of # of protein coding genes across species
Is there a correlation between non-coding DNA amount and organismal complexity?
yes, strong correlation. most of the increase in genome size comes from introns and intergenic regions.
What is the selfish DNA hypothesis?
TEs contribute to the genome size evolution
What is the bulk DNA hypothesis?
DNA is under direct selection for structural reasons
What is the metabolic cost hypothesis?
small genome is more energetically efficient & allows faster genome replication
What is true about the selfish DNA hypothesis, bulk DNA hypothesis, & metabolic cost hypothesis?
all have supporting evidence but none conclusive
What is genome size reduction?
process by which an organism’s genome shrinks relative to that of its ancestors. seen in mitochondria plastid, host restricted bacteria, free living bacteria, & free living animals (birds, bats)
What are the dynamics of genome size evolution in birds and mammals?
- extensive lineage-specific TE insertions and DNA deletions 2. “accordion” model of genome size evolution (DNA loss counteracting TE expansion) 3. extensive DNA loss in birds & bats is responsible for maintaining compact genomes
Why does genome size increase?
due to introns and transposons, not protein coding genes
What is true about the stable genome sizes in mammals and birds?
they are dynamic
What is horizontal (lateral) gene transfer?
acquiring genes from other species. more common in prokaryotes. also happens in eukaryotes (e.g. mitochondria)
What are the 2 mechanisms of WGD?
- autopolyploidization - WGD w/i one species 2. allopolyploidization - hybridization of 2 species
Describe the phylogenetic distribution of WGD events.
common in plants, rare in animals. S. cerevisiae (yeast). verts: 2R hypothesis ( 2 rounds of polyploidization ~500 MYA)
How long do duplicated genes from WGD last? Why?
longer than other gene duplications: 1. in WGD stoichiometric relationships btwn a gene and all of its interacting partners are preserved 2. WGD involves a complete duplication of surrounding regulatory seqs
What is the effect of WGD on speciation?
species that undergo WGD are more prone to speciation under gene duplication model of speciation. WGD may have contributed to the origin of major animal phyla
What is segmental duplicaiton (SD)/low copy # repeat (LCR)?
> 5,000bp, >90% seq indentity, <50 copies
What is neofunctionalization of duplicate genes?
one gene copy acquires a beneficial mutation that results in a new function (ex: human alpha- and beta-globin gene clusters adopted new function)
What is subfunctionalizaiton of duplicate genes?
2 gene copies partition the functions of the ancestral gene. one common molecular mechanism is partitioning of gene expression patterns
What does gene domain duplication & shuffling create?
new genes from existing genes