Lecture - 20 Mutations - DNA Repair

Question 1

5-bromouracil resembles which base?

Answer 1

Thymine

Question 2

5-bromouracil can lead to what?

Answer 2

replication error, by mispairing with guanine through wobble mechanism

Question 3

Alkylating agents do what?

Answer 3

donate an alkyl group

Question 4

What is a deamination agent

Answer 4

Nitrous acid

Question 5

What do Hydroxylamine groups do?

Answer 5

add hydroxyl groups

Question 6

Oxidative reaction species include?

Answer 6

Hydrogen peroxide - cause mispairings

Question 7

Intercalating agents include?

Answer 7

proflavin, acridine orange, and ethidium bromide - insert between adjacent bases in DNA, disrupt 3D structure

Question 8

Ionizing radiation does what?

Answer 8

dislodges electrons in tissue, cause increase of free radicals

Question 9

UV light does what?

Answer 9

Causes formation of thymine dimers

Question 10

What is the purpose of the Ames test?

Answer 10

to detect mutagens, use bacteria that cannot synthesize histidine

Question 11

What is mismatch repair?

Answer 11

first line of defense for incorrectly inserted nucleotides that escape proofreading. Strand with error is removed via exonucleases, DNA polymerase then replaces nucleotides. DNA ligase seals the knick.

METHOD OF NEW STRAND IDENTIFICATION IN EUKARYOTES IS CURRENTLY UNKNOWN

Question 12

Cologuard cancer screening test identifies what?

Answer 12

highly methylated DNA in the promotor of tumor suppressor genes.

Question 13

How does Base-Excision repair function?

Answer 13

Specific glycosylase recognizes specific modified base, endonuclease cleaves backbone and removes base, DNA polymerase adds new nucleotide, DNA ligase seals the knick.

Question 14

How does nucleotide-excision repair (NER) function?

Answer 14

Removes bulky DNA lesions, like pyrimidine dimers, that distort the double helix. The distortion is cut out and polymerase and ligase restore the original sequence.

NER FUNCTION DETERIORATES WITH AGE

Question 15

Which repair mechanisms is found in all organisms examined to date?

Answer 15

NER

Question 16

What are the two double stranded break repair mechanisms? which one uses a template?

Answer 16

Homologous recombination and Non-Homologous end joining. Homologous recombination uses a template, this makes it more accurate than NHEJ.

Question 17

Translesion DNA Polymerases allow what?

Answer 17

allow polymerases to skip over distortions/dimers, usually lead to mutation.

Question 18

Bloom syndrome is characterized by what?

Answer 18

growth deficiency, sun-sensitivty, predisposition to malignancy, telangiectatic

Question 19

Xeroderma Pigmentosum is characterized by what?

Answer 19

Abnormal skin pigmentation and acute sensitivity to sunlight. Strong predisposition to sunlight.

Question 20

Cockayne Syndrome and Trichothiodystrophy are characterized by what?

Answer 20

No increased risk of cancer, multiple developmental and neurological problems.

Question 21

This condition is responsible for about 15% of colon cancers?

Answer 21

Hereditary Nonpolyposis Colon Cancer