Lecture 8: Genome Evolution Flashcards Preview

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Flashcards in Lecture 8: Genome Evolution Deck (21)
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1
Q

Is there a correlation between C value and “complexity?”

A

no

2
Q

What reason supports the idea that more genes are needed for greater organismal complexity?

A

plants and animals independently increase genome sizes - suggest more cell types needs more genes

3
Q

Is there a correlation of coding DNA amount and organismal complexity?

A

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

4
Q

Is there a correlation between non-coding DNA amount and organismal complexity?

A

yes, strong correlation. most of the increase in genome size comes from introns and intergenic regions.

5
Q

What is the selfish DNA hypothesis?

A

TEs contribute to the genome size evolution

6
Q

What is the bulk DNA hypothesis?

A

DNA is under direct selection for structural reasons

7
Q

What is the metabolic cost hypothesis?

A

small genome is more energetically efficient & allows faster genome replication

8
Q

What is true about the selfish DNA hypothesis, bulk DNA hypothesis, & metabolic cost hypothesis?

A

all have supporting evidence but none conclusive

9
Q

What is genome size reduction?

A

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)

10
Q

What are the dynamics of genome size evolution in birds and mammals?

A
  1. 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
11
Q

Why does genome size increase?

A

due to introns and transposons, not protein coding genes

12
Q

What is true about the stable genome sizes in mammals and birds?

A

they are dynamic

13
Q

What is horizontal (lateral) gene transfer?

A

acquiring genes from other species. more common in prokaryotes. also happens in eukaryotes (e.g. mitochondria)

14
Q

What are the 2 mechanisms of WGD?

A
  1. autopolyploidization - WGD w/i one species 2. allopolyploidization - hybridization of 2 species
15
Q

Describe the phylogenetic distribution of WGD events.

A

common in plants, rare in animals. S. cerevisiae (yeast). verts: 2R hypothesis ( 2 rounds of polyploidization ~500 MYA)

16
Q

How long do duplicated genes from WGD last? Why?

A

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

17
Q

What is the effect of WGD on speciation?

A

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

18
Q

What is segmental duplicaiton (SD)/low copy # repeat (LCR)?

A

> 5,000bp, >90% seq indentity, <50 copies

19
Q

What is neofunctionalization of duplicate genes?

A

one gene copy acquires a beneficial mutation that results in a new function (ex: human alpha- and beta-globin gene clusters adopted new function)

20
Q

What is subfunctionalizaiton of duplicate genes?

A

2 gene copies partition the functions of the ancestral gene. one common molecular mechanism is partitioning of gene expression patterns

21
Q

What does gene domain duplication & shuffling create?

A

new genes from existing genes