T4M4- DNA mutations and applied lecture

Question 1

are mutations always bad?

Answer 1

no they can cause either destructive cellular responses, beneficial adaptations or be perfectly harmless

Question 2

what can mutations be a result of

Answer 2

environmental factors, spontaneous mutations or error in DNA replication

Question 3

what are the most common types of mutations?

Answer 3

spontaneous

Question 4

do viruses have low or high mutation rate?

Answer 4

high

Question 5

why are RNA viruses more prone to mutation

Answer 5

due to delicate nature of backbone
- no proofreading capability

Question 6

what will happen to a division of cell with mutation?

Answer 6

new cell will have part of mutation

Question 7

what happens if a mutation occurs in non dividing (post mitotic) cell in G0 phase?

Answer 7

effect of mutation is negligible

Question 8

are mutations inherited in somatic cells?

Answer 8

no

Question 9

are mutations inherited in germ cells? why

Answer 9

yes because germ cells produce offspring

Question 10

what did joshua and esther lederberg’s experiment in 1952 show

Answer 10

mutations are random and not directed

Question 11

what type of nutrients were in the experimental setup of lederberg

Answer 11

nonselective supplemented nutrients
- so that cell can grow and form bacteria

Question 12

what was in the new selective plate?

Answer 12

antibiotic penicillin

Question 13

what is this process of stamping called

Answer 13

replica pleating
- preserves relative arrangements of colonies relative to original plate

Question 14

what did they find after stamping

Answer 14

only few colonies survived penicillin on plate 2

Question 15

what did they predict about the new colonies that survived

Answer 15

carry mutation resistant to antibiotic for penicillin

Question 16

what does the process of replica mean

Answer 16

original colony isolated from original agar and used to test

Question 17

after testing what did they discover about the mutations?

Answer 17

it existed in population prior to exposure

Question 18

what can repair breaks in DNA backbone?

Answer 18

DNA ligase

Question 19

why do most cells contain DNA ligase

Answer 19

for replication and repair of single stranded breaks

Question 20

define proofreading

Answer 20

scanning DNA for potential mismatches

Question 21

what does a mismatch cause

Answer 21

kink in DNA molecule

Question 22

what causes a single stranded cleavage of mismatched DNA in the backbone

Answer 22

nuclease

Question 23

what happens once nuclease cuts the backbone

Answer 23

another enzyme removes successive nucleotides from DNA strand

Question 24

what happens if DNA accidently incorporates uracil

Answer 24

DNA-uracil glycosylase will cleave uracil from backbone, leaving deoxyribose sugar with no base

Question 25

what is the lack of base detected by

Answer 25

AP endonuclease

Question 26

what does AP endonuclease do

Answer 26

cleaves backbone of lack based area, leaving gap for addition of new nucleotide

Question 27

what happens in a base excision repair

Answer 27

damaged base is recognized and removed from the DNA backbone by one of the DNA glycosylases

Question 28

what is nucleotide excision repair similar to

Answer 28

mismatch repair

Question 29

what does a nucleotide excision repair do

Answer 29

removes and replaces one or more nucleotide bases in a "cut and patch" way

Question 30

how are bases cleaved during nucleotide excision repair

Answer 30

bases signal to enzymes to cleave DNA backbone on both sides of damaged bases

Question 31

what are small point mutations

Answer 31

single nucleotide pair changes

Question 32

where do small point mutations arise and why

Answer 32

during DNA replication due to escaping proofreading mechanisms

Question 33

what are the most common types of small point mutations

Answer 33

single nucleotide base substitution

Question 34

what is another name for single nucleotide base substitution

Answer 34

single nucleotide polymorphisms or SNP

Question 35

what mutation causes sickle cell anemia

Answer 35

a missense mutation that causes a single amino acid substitution in the hemoglobin molecule

Question 36

what happens as a result of the base change in sickle cell anemia

Answer 36

translation of valine instead of glutamate

Question 37

define missense mutation

Answer 37

when a single nucleotide base is changed, resulting in a a different amino acid

Question 38

define silent mutation

Answer 38

occurs when a change in nucleotide pair has codon substitute but still produces same amino acid - possible due to gene redundancy

Question 39

what do most substitution mutations lead to

Answer 39

missense mutations

Question 40

what is a nonsense mutation

Answer 40

a point mutation which gives rise to an amino acid which codes for stop codon

Question 41

describe result of nonsense mutations

Answer 41

-causes premature translation termination -has shorter polypeptide sequence -can lead to nonfunctional proteins

Question 42

define insertion

Answer 42

when one or more extra nucleotide is inserted into replicating DNA

Question 43

define deletion

Answer 43

skipping or removing more than one nucleotide during replication

Question 44

what determines degree of impact of insertion or deletions

Answer 44

size of mutation

Question 45

what mutation causes cystic fibrosis

Answer 45

deletion of 3 nucleotides in CFTR channel

Question 46

define a frameshift mutation

Answer 46

occurs when insertion or deletion does not happen in a group of three

Question 47

what does a frameshift mutation lead to

Answer 47

-improper grouping of nucleotides -massive missense mutations -ends in nonsense and nonfunctional proteins

Question 48

what happens when a centromere is lost

Answer 48

entire chromosome is lost because not allocated into daughter cells

Question 49

what happens if there is a deletion in one homologous chromosome

Answer 49

organism may persist depending on if other homologue can compensate to provide gene product needed for survival

Question 50

what can chromosomal duplication cause

Answer 50

little harm due to homologous chromosome

Question 51

what can duplication lead to

Answer 51

new gene being formed with similar function to original gene

Question 52

define inversion

Answer 52

when normal sequence is reversed

Question 53

what causes an inversion?

Answer 53

a segment breaks off and reattaches in reverse order

Question 54

is inversion serious?

Answer 54

no because all genes are present

Question 55

what does inversion explain?

Answer 55

long term chromosomal evolution

Question 56

define reciprocal translocation

Answer 56

portion of one chromosome attach to non homologous chromosome and exchange terminal chromosomal fragments

Question 57

when does reciprocal translocation occur

Answer 57

happens when there is a break and translocation carried out before the break required

Question 58

where does reciprocal translocation occur

Answer 58

in non coding regions of DNA in large genome

Question 59

explain duplication and divergence effect with globin proteins in fetuses

Answer 59

two gamma globin genes are almost identical in amino acid sequence but expressed at different points

Question 60

explain duplication and divergence effect with globin proteins in adults

Answer 60

adult delta and beta hemoglobin differ in amino acid sequence and are expressed at different levels

Question 61

what are miRNAs

Answer 61

microRNAs- short non coding RNA that regulate gene expression post transcriptionally

Question 62

what are TUFs

Answer 62

transcripts of unknown function- their role in the cell is unknown

Question 63

what does the alternative splicing hypothesis state

Answer 63

eukaryotes do not require large numbers of distinct genes

Question 64

how similar are chimp and human genes?

Answer 64

98.8%

Question 65

where are the differences in genome found between chimps and humans

Answer 65

in the regulatory sequences - responsible for phenotypic differences