Oct 9\

Question 1

What is a replicator and replicon?

Answer 1

Replicator is part of DNA sequence that transcription is initiated on, it is AT rich. Replion is DNA replicated from that origin

Question 2

How many proteins make up the origin recognition complex (ORC)?

Answer 2

6 of them

Question 3

What sites on replicator?

Answer 3

B2 for helicase recruiters to bind to. B1 and A are the ORC binding site

Question 4

What is passive activation of replicators?

Answer 4

It is when origins close by activated, the replication bubble grows and transcribes that part of the other replicators too

Question 5

What happens in G1 to prep for transcription?

Answer 5

Cell selects replicators, and starts building ORC complex, does not start replication until S phase

Question 6

How helicase loaded?

Answer 6

ORC complex binds when ATP hydrolyzed, then helicase binding proteins recruited by ORC C. 2 Helicase subunits bind to recruiters. When ATP hydrolysis on cdc6, helicase wraps around dsDNA. Then when activated, each part separates, only on ssDNA

Question 7

How is ORC complex activated?

Answer 7

CDK PO4s Sld2/3, and DDK PO4s helicase. Then poly epsilon is recruited, then cdc45 and GINS recruited (helicase activator proteins). THen replication starts, then primase and DNA pol delta recruited to newly formed replication bubble

Question 8

How CDK levels affect helicase? Which parts of cell cycle?

Answer 8

When levels low, helicase can be loaded onto DNA. When high, now it can be activated, and also can not be loaded onto DNA. low in G1, High in S phase, G2, and Mitosis to prevent new helicase binding so only 1 transcription per cell cycle

Question 9

Is plasmit done bi or uni directionally? What separates the 2 rings after transcritpion

Answer 9

Bi. The 2 rings are separated with topo 2 after

Question 10

What is solution (2) for end replicaton problem?

Answer 10

Use proteins with 3’OH end to have dNTPs added to it, not degraded. Or use telomeric sequence

Question 11

What is telomeric sequence rich in and how does telomerase work?

Answer 11

TG rich. Telomerase is ribonucloproten complex, has RNA subunit so no exogenous DNA needed. It also has reverse transcriptase. It 1.5 copies of telomeric sequence, and its own RNAis used as template. Then translocates so only partially covering old strand, then extends old strand with its sequence to make ssDNA from its RNA (reverse transcription)

Question 12

WHat are telomere binding proteins?

Answer 12

They bind to telomeres, inhibit telomerase activit, protect telomeres from DNA repairing enzymes

Question 13

Why do telomeres form t-loops?

Answer 13

So the ends can’t be degraded by DNA repair mechanisms