Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MBG 2040 > Genetic Mutations and DNA Repair > Flashcards

Genetic Mutations and DNA Repair Flashcards

Lectures 10-13

1
Q

what is a mutation?

A

a heritable change in an organism’s genetic material that may alter the phenotype of the organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is a mutant?

A

an organism that carrier one or more mutations in their genetic material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how are mutations and evolution related?

A

mutation is the source of all genetic variability
natural selection preserves the best adapted
recombination between homologous chromosomes creates more variability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the types of genetic mutations?

A

SOMATIC: will not be transmitted to progeny
GERM: transmitted to progeny via GAMETE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is transition mutation?

A

replaces a pyrimidine with another pyrimidine or a purine with a purine

SAME

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is a transversion mutation?

A

replaces a pyrimidine with a purine or vice versa

DIFFERENT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are frame shift mutations?

A

insertion or deletion, shifting the reading frame
mutant DNA –> mutant mRNA –> WRONG PROTEINS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are TAUTOMERIC shifts?

A

a rare REVERSIBLE change in the location of a hydrogen atom on a NT

=O (keto) –> -OH (enol)
-NH2 (amino) –> =NH (immino)

can cause A=C pairs and GT pairs (triple bond)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how many mutant daughter strands will you get in the second progeny of a tautomeric shift?

A

1/4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are expanding nucleotide repeats?

A

repeats in a triplet codon
(ex. supposed to be 30 repeats, now there are 50)
caused by a hairpin structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is a MISSENSE mutation?

A

a base substitution that results in an AA change in the protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is a NONSENSE mutation?

A

base substitution that codes for a STOP codon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is a SILENT mutation?

A

a base substitution where the changes in the codon still specify the SAME AA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is a loss of function mutation?

A

results in complete or partial loss of normal protein function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is a gain of function mutation?

A

produces a protein or a gene product who’s function is not normally present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is a conditional mutation?

A

expressed under CERTAIN (environmental) conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is a lethal mutation?

A

causes premature cell death

18
Q

what is a SUPPRESSOR mutation?

A

mutation at a SECOND SITE that hides or suppresses the effect of the first mutation

INTRAGENIC = same gene
INTERGENIC = different gene

NOT a reverse mutation

19
Q

what factors affect mutation rates?

A

DNA wrapped around HISTONES have FEWER mutations

frequency, probability, detection

20
Q

describe mispairing due to other structures

A

shifts in the helix or PROTONSTION of bases can allow DIFFERENT BASES TO BOND

can arise from WOBBLE (nonstandard base pairing in 3rd codon)

21
Q

what are INCORPORATED errors?

A

base substitution causes a mis-paired base to be incorporated into the strand
repair system cannot correct this

22
Q

what can cause insertion or deletion mutations?

A

crossing over
strand slippage (forms a loop in template OR new strand)

23
Q

what is depurination?

A

loss of a purine base from a NT
breakage of covalent bond between purine base a 1’C atom of sugar
A is most often incorporated into the base, causing a permanent mutation

24
Q

what is demaination?

A

cytosine loses its NH2 group and BECOMES URACIL and will pair with ADANINE (C–>T transition)

methylated cytosine will become THYMINE (C–>T transition)

25
Q

what are BASE ANALOGS?

A

chemicals with similar structures to the 4 NTs

5-BROMOURACIL is an analog of thymine that can pair with guanine (A –> G transition)

2-AMINOPURINE is a base analog of adenine that mis pairs with CYTOSINE (T –> C transition)

26
Q

what are ALKYLATING AGENTS?

A

add METHYL or ETHYL groups to bases

ex. ETHYLMETHYLSULFONATE (EMS) and MUSTARD GAS

adds ethyl group to guanine, causes it to pair with thymine (G–>A transition)
adds an ethyl group to thymine, causes it to pair with guanine (T–>C transition)

27
Q

what are DEAMINATING chemicals

A

removes a NH2 group

NITROUS ACID

causes transition mutations

28
Q

what is HYDROXYLAMINE?

A

adds hydroxyl groups to cytosine
increased occurance of tautomer that pairs with adenine
C–>T transition

29
Q

what are OXIDATIVE RADICALS?

A

reactive forms of oxygen
produced by metabolism
causes TRANSVERSION mutations

REMEMBER: oxidatiVe, transVersion (the Vs go together)

30
Q

what are INTERCALATING agents?

A

ETHIDIUM BROMIDE, ACRIDINE ORANGE, DIOXIN, PROFLAVIN
sandwiches between base pairs
distorts helix
causes FRAMESHIFT mutations

31
Q

how do X rays cause mutations?

A

produce IONIZING radiation
dislodge electrons from atoms
produce free radicals
breaks phosphodiester bonds –> double stranded breaks

32
Q

how does UV cause mutations?

A

PYRIMIDINES absorb UV light
induces chemical bond between two adjacent pyrimidines (STOP signal)
causes thymidine dimers

33
Q

what are the two general features of DNA repair?

A

complimentary strand acts as a TEMPLATE for the one being repaired

DNA repair has REDUNDANCY

34
Q

describe mismatch repair

A

old strand has methyl group at GATC sequence –> allows for differentiation

mismatch repair (MMR) complex brings the mismatch sequences close to the GATC sequence (forms a loop) and nicks

polymerase and ligase fill the gaps

mutations in MMR can lead to cancer

35
Q

what is direct repair?

A

PHOTOLAYSE breaks bonds between thymine dimers caused by UV light

O6-methylguanine-DNA methyltransferase removes methyl group from methylated guanine

36
Q

describe base excision repair

A

DNA glycosylase removes JUST the damaged base

creates an apurinic/apyrimidinic (AP) site

AP endonuclease cleaves phosphodiester bond

deoxyribose sugar removed

DNA polymerase fills in the gap and ligase seals gaps

37
Q

describe NUCLEOTIDE excision repair

A

an enzyme complex recognizes the damage distorting the DNA helix

DNA strand is separated, SSBPs stabilize the strand

enzymes cleaves mutated strand, helicase removes it

gap is sealed by polymerase and ligase

38
Q

describe the mutations caused by DOUBLE STRANDED BREAKS

A

stalls DNA replication, which could cause chromosomal rearrangements

39
Q

describe HOMOLOGY DEPENDANT repair

A

homologous chromosomes align

NTs enzymatically removed, producing what looks like sticky ends

a free 3’ invades and displaces a strand of unbroken DNA and elongates

displaced strand forms a loop, which pairs with the broken DNA molecule

DNA synthesis occurs, strand attachment produces holiday junctions

40
Q

describe NONHOMOLOGOUS END JOINING

A

often happens during G1 phase

more error prone

Ku proteins detect the breaks and call polymerase and ligase to fix whatever breaks they can

MBG 2040 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions