Plasticity

Question 1

where do new ALLELES come from

Answer 1

mutations

Question 2

what kinds of mutations can create new alleles

Answer 2

• alterations to DNA that escape repair BEFORE replication
• copying error DURING rplication

Question 3

do mutations always cause a visible change to a phenotype?

Answer 3

• no
• sometimes they may be in a noncoding region that does not affect the amino acid produced

Question 4

explain DNA repair

Answer 4

mutations a common but most are repaired by mismatch repair enzymes and proofreading enzymes

Question 5

how does a mutation in the DNA affect the amino acid

Answer 5

1. point mutations
2. indels

Question 6

mutation in the DNA - point mutation

Answer 6

• the substitution of one base for another
• can be silent, nonsynonymous (missense), or nonsense

Question 7

point mutation - silent mutation

Answer 7

• no change in the amino acid
• produces a normal protein

Question 8

point mutation - nonsynonymous mutation

Answer 8

• change in the amino acid
• produces an abnormal protein

Question 9

point mutation - nonsense mutation

Answer 9

• premature stop codon
• produces an incomplete, nonfunctional protein

Question 10

mutation in the DNA - indels

Answer 10

• insertion (mutation in introns)
• deletions (mutation in exons)
• both results in a large scale frame shift

Question 11

indels - large scale frame shifts

Answer 11

• shifts amino acids downstream
• results in new amino acid sequence
• resulting protein is unlikely to have any biological activity

Question 12

what type of mutation should matter most for evolution?

Answer 12

• nonsynonymous
• the changes would be really subtle and could lead to a new function

Question 13

explain the rates of mutations

Answer 13

• they vary greatly from species to species
• each human has about 36 point mutations per parent (~70 mutations per individual)
• mutation rates can evolve

Question 14

where do new GENES come from?

Answer 14

• gene duplication
• new genes from scratch (some are born from noncoding DNA)

Question 15

new genes - gene duplication

Answer 15

• should not affect phenotype
• its neutral but has the potential to create diversity and it may not be advantageous
• can happen via: unequal crossing over and retroposition or retroduplication

Question 16

gene duplication - what happens in normal crossing over

Answer 16

• recombination
• occurs in prophase in meiosis I
• creates chromosomes with new combination alleles
• generates diversity

Question 17

gene duplication - unequal crossing over

Answer 17

it is an error in the genetic recombination that happens during meiosis resulting in gene duplication

Question 18

gene duplication - retroposition/retroduplication

Answer 18

• a processed mRNA (with the introns already spliced out) is reverse-transcribed by the enzyme reverse transcriptase to form DNA
• if this DNA integrates into one of the main chromosomes, the genome acquires a duplicated copy of the original gene

Question 19

why is gene duplication important for evolution

Answer 19

• allows mutation to occur in a new gene while still retaining the original function
• gene duplication followed by divergence results in a new functional gene
• more of the genome is affected by copy number variation than point mutations

Question 20

chromosome mutations

Answer 20

• inversions
• whole genome duplication

Question 21

chromosome mutations - inversions

Answer 21

results when a chromosome segment breaks in two places and reanneals with the integral segment reversed

Question 22

chromosome mutations - why do inversions matter

Answer 22

• breaks up linkage groups
• breaks new linkage groups
• creates supergenes which allows selection to act on groups of alleles

Question 23

chromosome mutations - whole genome duplication

Answer 23

• if homologous chromosomes fail to segregate during meiosis I or if sister chromatids do not separate properly during meiosis II
• resulting cells may have double the number pf chromosomes of the parent cell

Question 24

whole genome duplication - what is polyploid

Answer 24

organisms with more than two chromosome sets

Question 25

generally explain the process of whole genome duplication

Answer 25

- starts with 2n, then mutates to become 4n - self-fertilization creates another 4n in the second generation

Question 26

why is whole genome duplication important for evolution and speciation

Answer 26

- the diploid parent cannot reproduce with the tetraploid offspring - results in reproductive isolation and speciation

Question 27

how do mutations affect fitness

Answer 27

- mutations can be lethal, deleterious, neutral, or beneficial - lethal and deleterious outnumber neutral and beneficial

Question 28

how do mutations affect fitness - what would happen if there was no selection

Answer 28

organisms will die bc selection takes out deleterious mutations

Question 29

explain the mutation-selection balance

Answer 29

selection balances mutations which can be a majority deleterious