Mutagens & Mutations

Question 1

what is a free radical

Answer 1

unstable molecule with an unpaired outer electron

fragments of broken biomolecules

Question 2

how do free radicals come to be?

Answer 2

normal metabolism

inflammation

UV light/ionizing radiation

tobacco smoke, pollutants in air/water

Question 3

ROS

Answer 3

reactive oxygen species

Question 4

how do we deal with free radicals?

Answer 4

cells have enzyme detox systems

convert oxygen free radicals into O2 + water

Question 5

mutagenic chemicals

Answer 5

attack DNA specifically

moldy peanuts fungal toxin: aflatoxin

sulfur mustard

Question 6

mutagenic chemicals used to create new mutations

Answer 6

ethylnitrosourea and ethylmethanesulfonate

react with bases to cause lesions

could be used to kill dividing cancer cells in chemo

Question 7

two kidns of electromagnetic radiation that affect DNA

Answer 7

UV: base dimers

ionizing: xray/gamma ray

Question 8

particulate radiation

Answer 8

strongly ionizing

inhalation of radioactive radon gas (55%)

basements cut from solid rock accumulate radon

Question 9

chemicals in food

Answer 9

dark meat is a source of carcinogens

processed meat that has preservatives/nitrates

childhood leukemia (hotdogs)

Question 10

5 effects of a mutation inside an ORF

Answer 10

silent

missense

nonsense

codon gain/loss

frameshift

Question 11

point mutations cause what kind of effects

Answer 11

silent

missense

nonsense

Question 12

silent mutation

Answer 12

point mutation that does not change the meaning of a codon (no coding change)

Question 13

missense mutation

Answer 13

point mutation that change one amino acid to another

coding change

Question 14

nonsense mutation

Answer 14

point mutation that turns an amino acid codon into a stop codon

18 codons are 1 base away from stop

Question 15

which two mutation effects are caused by insertions or deletions?

Answer 15

codon gain/loss and frameshift

in frame: deletion/insertion of 3 bases causes codon gain/loss

frameshift: deletion/insertion of anything other than 3 bases

Question 16

codon gain/loss

Answer 16

inserts or deletes 3 nucleotide bases (1 aa)

Question 17

frameshift

Answer 17

changes all downstream codons and causes a new termination point

can cause a protein of any length

Question 18

neutral aa changes

Answer 18

some aa changes and gains/losses do not affect protein function

Question 19

other effects of small mutations

Answer 19

effects: intron splice sites

regulatory sites inside or outside of transcription units

Question 20

effects on intron splice sites

Answer 20

introns begin with GU (RNA)/ GT and end with AG

this is how a splicosome knows where to cut

if mutate either code, might splice wrong bit

Question 21

effect on regulatory site outside of transcription unit

Answer 21

relates to CRM

may affect TF binding site so it doesn’t bind, phenotypic effect

Question 22

unequal crossing over and strand slippage produce…

Answer 22

duplicated sequences

unequal crossing over: meiosis

strand slippage: DNA replication

Question 23

variable number tandem repeat VNTR

Answer 23

places in DNA where same short sequence of bases is repeated in multiple tandem copies

variation in individuals btw # of copies

unequal crossing over in meiosis requires a recombination at the VNTR site

Question 24

are VNTR sites protein coding?

Answer 24

no, function is not clear

Question 25

DNA fingerprinting

Answer 25

VNTR genotypes are the basis b/c differ in each individual

Question 26

triplet repeat expansions

Answer 26

a set of genetic diseases where expansion multiplies repeats within a gene

DNA replication

repeats can be in an ORF or UTR