DSA Facts

Question 1

Phosphodiester bond is between what carbons in DNA?

Answer 1

between 3’C of a sugar and 5’C of the next

Question 2

…………form of DNA is the most common. It is a right-handed helix. It has an axis of symmetry, antiparallel pairing, and is complementary.

Answer 2

B

Question 3

The A form of DNA is a wide right handed spiral found in what?

Answer 3

dehydrated samples of DNA, DNA-RNA hybrids, enzyme-DNA complexes

Question 4

What is the Z form of DNA involved in?

Answer 4

transcription initiation and regulation extensive methylation

Question 5

Alkali and heat can separate DNA strands. How does each work?

Answer 5

● Alkali breaks phosphodiester bond in RNA ● Heat (Tm) converts dsDNA to ssDNA via denaturation/melting

Question 6

Major and minor grooves between the strands of DNA allow for binding of what?

Answer 6

Regulatory proteins (transcription factors), antibiotics, and anticancer drugs

Question 7

Prokaryotic DNA is in the nucleoid, where DNA is supercoiled and attached to RNA-protein. What structure do eukaryotes have that prokaryotes don’t?

Answer 7

Histones/nucleosomes

Question 8

8 histones (basic AAs) → nucleosome core → solenoid (30nm chromatin fiber). What does the chromatin fiber do?

Answer 8

anchors to the nuclear scaffold

Question 9

Do Histone acetyltransferases (HATs) make DNA accessible or unaccessible?

Answer 9

accessible

Question 10

What do Histone deacetylases (HDACs) do?

Answer 10

Inactivate chromatin

Question 11

rRNA makes up the most RNA. What are the components of rRNA for both proks and euks?

Answer 11

● Pro: 70S = 50S + 30S ● Euk: 80S = 60S + 40S

Question 12

What do miRNA (Micro RNA) do?

Answer 12

non-coding nucleotides that repress protein biosynthesis via: ■ Preventing ribosomes from binding to mRNA ■ Degrading mRNA

Question 13

What do lncRNA (long noncoding RNA) do?

Answer 13

partake in epigenetic DNA modifications, such as X inactivation.

Question 14

What do lincRNA (large intergenic noncodingRNA) do?

Answer 14

scaffold DNA-chromatin complexes Ex. HOTAIR overexpressed in breast tumors

Question 15

What are the 2 nucleotide analogs used to treat cancer?

Answer 15

■ Azacitidine (Vidara) ■ 5-fluorouracil

Question 16

Azacitidine (Vidara) is the nucleotide analog used to treat………………….. It Interferes with polyribosome assembly and tRNA recognition, and covalently binds to and causes degradation of DNA methyltransferase.

Answer 16

myelodysplastic syndrome

Question 17

5-fluorouracil is the nucleotide analog used to treat………………………… It irreversibly inhibits thymidylate synthase. Therefore, the body cannot synthesize thymine, and there is no DNA replication.

Answer 17

metastatic adenocarcinoma

Question 18

What nucleotide analogs are used to stop the synthesis of Viral DNA?

Answer 18

● AZT (Zidovudine) replaces hydroxyl group with azido group. It takes advantage of its higher affinity to reverse transcriptase than normal human DNA polymerases ● ddl (Didanosine) removes hydroxy group from deoxyribose ● Arabinose is a sugar used to replace deoxyribose

Question 19

What are the roles of the prokaryotic DNA polymerases?

Answer 19

Question 20

What parts of the cell cycle are considered interphase?

Answer 20

G1

S

G2

Question 21

What are the different cyclins associated with G1, S, and G2 phases of the cell cycle?

Answer 21

G1 - Cyclin D

S - Cyclin E & Cyclin A

G2 - Cyclin B

Question 22

What is the most important point for control in the cell cycle?

Answer 22

G1/S (Cyclin D1)

Question 23

The binding of cyclins activates the kinase activity of CDKs. Here is a picture to know:

Answer 23

Question 24

Explain how retinoblastoma protein and p53 regulate the progression of the cells cycle:

Answer 24

E2F is a transcription factor that is needed to drive the G1/S transition. Rb (tumor-suppressor) suppresses E2F by binding E2Fand creating inhibitory complex.

P53 (tumor-suppressor) is elevated in response to DNA damage (stress). It prevents cell growth by arresting at G1/S, activating DNA repair and Apoptosis. P53 (“guardian of the genome”) inhibits E2F-5, by initiating transcription of p21, which is a CKI (cyclin kinase inhibitor). It inhibits the phosphorylation of Rb, causing Rb to stay bound on E2F, and unable to perform transcription