Genes and Genomes

Question 1

natural variation in genome size is

Answer 1

extreme - known genome sizes range by over 6 orders of magnitude

Question 2

more complex organisms tend to have

Answer 2

more genes, but not proportionately and with some large outliers

Question 3

viral and bacteria genomes

Answer 3

usually incredibly compact

Question 4

eukaryotes (esp multicellular) have more

Answer 4

non-genic DNA

Question 5

how do new genes arise?

Answer 5

gene/domain/genome duplications
horizontal gene transfer
de novo genes

Question 6

mechanisms of gene/domain duplication

Answer 6

unequal crossing over
DNA polymerase slippage
retrotranscription

Question 7

neofunctionalization

Answer 7

at least one copy of a duplicated sequence gains a new function

Question 8

subfunctionalization

Answer 8

a duplicated sequence loses some of its pleiotropic roles

Question 9

methods of horizontal gene transfer

Answer 9

bacteria swap genes constantly, viruses can leave genes in their host genome, and endosymbionts + hosts exchange genes over generations

Question 10

de novo genes

Answer 10

brand new genes emerging from non-coding sequences, if a regulatory mutation arises that activates transcription

Question 11

pseudogene

Answer 11

gene remnant after degradation of a gene duplicate
speed of their degradation is useful as a reference point for a neutrally evolving segment of genome

Question 12

how are genes lost

Answer 12

degradation after duplication, unequal crossing over, slippage, and transposable elements

Question 13

gene families are actively ______ in any lineage due to drift and selection

Answer 13

expanding and contracting

Question 14

loss, gain, or divergence of a duplicated gene is more likely to be fixed if the gene is

Answer 14

adaptive

Question 15

dN/dS

Answer 15

ratio of nonsynonymous mutations to synonymous

Question 16

dN/dS = 1

Answer 16

all sites are evolving neutrally

Question 17

low dN/dS ratio

Answer 17

purifying selection - nonsynonymous mutations are being quickly removed

Question 18

high dN/dS ratio

Answer 18

positive select - nonsynonymous mutations are being selected for and sweeping

Question 19

concerted evolution by gene conversion

Answer 19

in a stretch of repeated segments, a mutation in one copy can spread to the others

Question 20

retrotransposition

Answer 20

the mRNA of a gene is reverse-transcribed into DNA and then becomes part of the genome

Question 21

only x % of the genome is coding sequences in multicellular eukaryotes

Answer 21

2%

Question 22

introns

Answer 22

allow for alternative splicing

Question 23

heterochromatin

Answer 23

participates in gene regulation

Question 24

transposons in humans

Answer 24

very few are currently active, but lots are recently active
ex. Alu transposon

Question 25

active transposons

Answer 25

highly chaotic, can interrupt genes or regulatory regions, can create new combos of pre-existing gene elements may have been the origin of our spliceosome