PRIVETTE-VINNEDGE 2 Flashcards
What are the three phases of preparation for cell division in the cell cycle?
Interphase (G1, S, G2)
What are the growth phases of the cell cycle?
G1 and G2
What is the name of the DNA synthesis phase of the cell cycle?
S phase
What happens during the M phase of the cell cycle?
Mitosis (cell division)
How are transitions between the phases of the cell cycle regulated?
By cell cycle checkpoints
Where does DNA replication begin?
At distinct loci called Origins of Replication
What type of organisms have origins of replication with a consensus DNA sequence?
Prokaryotic organisms and yeasts
How do eukaryotic organisms identify origins of replication?
Based on contextual clues
What are three contextual cues that eukaryotic organisms use to identify origins of replication?
Local DNA topology; Chromatin modifications; DNA composition
What type of DNA sequence is usually found at origins of replication?
AT-rich sequence
What is the term for loosely packed chromatin that is open for transcription?
Euchromatin
What is the term for densely packed chromatin?
Heterochromatin
What type of chromatin is generally thought to be replicated first?
Euchromatin (early replication)
What type of chromatin is thought to be replicated later?
Heterochromatin (late replication)
What proteins bind to DNA origins of replication?
Origin recognition complex (ORC) proteins
What happens to many potential origins of replication in G1?
They are identified and primed, but only some “fire” and are used in S phase
How long does the S phase typically last?
8-10 hours
What proteins are involved in the E2F mediated transcription that occurs during the G1-S phase transition?
Cyclin-E and -A
What do Cyclin-E and -A activate?
CDK2
What does the CyclinE-CDK2 complex do to trigger the S phase?
It phosphorylates (inactivates) Rb
What roles do Cyclin E, Cyclin A, and CDK2 play in the S phase?
They have essential roles in initiating DNA replication
What is DNA origin licensing?
The process of identifying and preparing origins of replication for DNA synthesis
How many origins of replication are there per Mb of DNA?
25-40
What proteins bind to ORC during DNA origin licensing?
Cdc6 and Cdt1