DSA Facts Flashcards
(24 cards)
Phosphodiester bond is between what carbons in DNA?
between 3’C of a sugar and 5’C of the next
…………form of DNA is the most common. It is a right-handed helix. It has an axis of symmetry, antiparallel pairing, and is complementary.
B
The A form of DNA is a wide right handed spiral found in what?
dehydrated samples of DNA, DNA-RNA hybrids, enzyme-DNA complexes
What is the Z form of DNA involved in?
transcription initiation and regulation extensive methylation
Alkali and heat can separate DNA strands. How does each work?
● Alkali breaks phosphodiester bond in RNA ● Heat (Tm) converts dsDNA to ssDNA via denaturation/melting
Major and minor grooves between the strands of DNA allow for binding of what?
Regulatory proteins (transcription factors), antibiotics, and anticancer drugs
Prokaryotic DNA is in the nucleoid, where DNA is supercoiled and attached to RNA-protein. What structure do eukaryotes have that prokaryotes don’t?
Histones/nucleosomes
8 histones (basic AAs) → nucleosome core → solenoid (30nm chromatin fiber). What does the chromatin fiber do?
anchors to the nuclear scaffold
Do Histone acetyltransferases (HATs) make DNA accessible or unaccessible?
accessible
What do Histone deacetylases (HDACs) do?
Inactivate chromatin
rRNA makes up the most RNA. What are the components of rRNA for both proks and euks?
● Pro: 70S = 50S + 30S ● Euk: 80S = 60S + 40S
What do miRNA (Micro RNA) do?
non-coding nucleotides that repress protein biosynthesis via: ■ Preventing ribosomes from binding to mRNA ■ Degrading mRNA
What do lncRNA (long noncoding RNA) do?
partake in epigenetic DNA modifications, such as X inactivation.
What do lincRNA (large intergenic noncodingRNA) do?
scaffold DNA-chromatin complexes Ex. HOTAIR overexpressed in breast tumors
What are the 2 nucleotide analogs used to treat cancer?
■ Azacitidine (Vidara) ■ 5-fluorouracil
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.
myelodysplastic syndrome
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.
metastatic adenocarcinoma
What nucleotide analogs are used to stop the synthesis of Viral DNA?
● 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
What are the roles of the prokaryotic DNA polymerases?
What parts of the cell cycle are considered interphase?
G1
S
G2
What are the different cyclins associated with G1, S, and G2 phases of the cell cycle?
G1 - Cyclin D
S - Cyclin E & Cyclin A
G2 - Cyclin B
What is the most important point for control in the cell cycle?
G1/S (Cyclin D1)
The binding of cyclins activates the kinase activity of CDKs. Here is a picture to know:
Explain how retinoblastoma protein and p53 regulate the progression of the cells cycle:
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
