Quiz 2- Genomic Regulation

Question 1

Cross-linking chemical agents

Answer 1

Nitrogen mustard, cisplatin, mitomycin C, carmustine

Question 2

Alkylating agents

Answer 2

Dimethyl sulfate (DMS), methylmethane sulfonate (MMS)

Question 3

Intercalating agents

Answer 3

Thalidomide

Question 4

Drugs that inhibit HDACs, used as anticonvulsants and cancer drugs

Answer 4

Valproic acid and vorinostat

Question 5

DNA methylation

Answer 5

Typically represses gene transcription

Question 6

Acyclovir and AZT

Answer 6

Lack 3’ -OH group which, when added during RNA replication, acts as chain terminator in viruses

Question 7

UV radiation

Answer 7

Can produce covalent linkage (pyrimidine dimers)

Question 8

Ionizing radiation

Answer 8

Double strand breaks, chemical modification of bases, DNA-protein crosslinks

Question 9

Non-ionizing radiation

Answer 9

Sunlight can cause pyrimidine dimers

Question 10

Spontaneous DNA damage

Answer 10

Depurination (lose entire purine base, leaves sugar phosphate behind), deamination (adenine -> hypoxanthine or guanine -> xanthine or cytosine -> uracil), base deletion/substitution

Question 11

Methylated cytosine residues

Answer 11

Stably silences genes in CpG sites/islands (happens in cancers)

Question 12

Base excision repair

Answer 12

DNA glycosylase removes mismatched base (non-distorting mutation), AP endonuclease cuts phosphodiester bond, and DNA polymerase replaces correct nucleotide

Question 13

Nucleotide excision repair

Answer 13

Repairs distorted DNA shape (ex dimers). Strand unwound, damage nicked out with some other nucleotides. DNA polymerase fills in gap. Defects can lead to xeroderma pigmentosum

Question 14

Mismatch excision repair

Answer 14

MER complex binds to DNA at deformation, endonuclease cuts daughter strand w/ mutation and removes segment. Polymerase fills gap. Defects = hereditary nonpolyposis colorectal cancers

Question 15

Recombination: NHEJ and homologous recombination

Answer 15

For when DNA undergoes double stranded breaks.
NHEJ: ends joined together by DNA ligase, several base pairs at site missing
Homologous: genetic info from other chromosome (if happened during cell division) used to repair damage. (BRCA1/2 genes)

Question 16

Transcription-coupled repair

Answer 16

Type of NER initiated when RNA polymerase stalls at lesion in DNA template during transcription. ERcc-6 an ERcc-8 recruited (defects in these lead to cockayne syndrome severe growth defects)

Question 17

Translesion synthesis (bypass synthesis)

Answer 17

Caused by unrepaired thymine dimers. Uses DNA polymerase to add in adenine across from one thymine. Low fidelity - still have mutations

Question 18

Reduced/incomplete penetrance

Answer 18

Frequency that a gene manifests itself as a phenotype

Question 19

Locus heterogeneity

Answer 19

When many genes influence a phenotype

Question 20

Pleiotropy

Answer 20

When one gene influences two or more seemingly unrelated phenotypic traits

Question 21

Variable expressivity

Answer 21

The range of phenotypes seen between individuals with a specific genotype

Question 22

Polygenic inheritance

Answer 22

Traits in which variations are thought to be caused by the combined effects of multiple genes. Ex: height

Question 23

Multifactorial inheritance

Answer 23

When environmental factors cause variation in the trait. Threshold of liability must be crossed before the disease is expressed