Chapter 4 Lecture 4 - DNA Replication and cell cycle Flashcards
Steps to DNA Replication
- Double helix unwinds from histones
- Helix is opened by DNA Helicase, creating the replication fork
- DNA polymerase moves along each strand, reading the bases and adding complementary nucleotides
- In one strand, DNA polymerase moves toward the fork, in the other away from the fork in segments
- DNA ligase joins segments together in the one strand
- Process continues until entire DNA sequence is copied
What is the enzyme used to open the helix
DNA helicase
What enzyme reads strand and adds complementary nucleotides
DNA polymerase
In what direction does DNA polymerase work
In one strand, toward the replication fork, in the other away from the replication fork, but in small segments
What enzyme joins together segments completed by DNA polymerase
DNA ligase
What kind of replication (in terms of what is left) is DNA replication considered
Semi-conservative (new DNA is a combination of old and new)
What are the 4 phases of the cell cycle
G1, S, G2, M
What is another name for G1
First Gap Phase
What happens during G1
- Cell makes organelles
- Gains materials needed for DNA replication
- Protein synthesis
- NORMAL FUNCTION
What is another name for the S phase
Synthesis Phase
What happens during the S phase
Cell duplicates centrioles and DNA
What is another name for G2
Second Gap Phase
What happens during G2
- Cell grows
- Makes organelles
- Produces enzymes needed for cell division
What is another name for the M phase
Mitotic Phase
What happens during M phase
Cell replicates its nucleus, pinches off to form two identical daughter cells
Interphase
Every part of the cell cycle other than the mitotic phase
What are the three checkpoints in the cell cycle
- Cell growth checkpoint
- DNA synthesis checkpoint
- Mitosis checkpoint
When and what happens during the Cell Growth checkpoint
End of G1, checks if cell is big enough and has the proper proteins
What happens if the cell growth checkpoint is not passed
Cell goes into G0 resting phase
When and what happens at the DNA synthesis checkpoint
During S phase, checks if DNA is replicated correctly, if yes, then it continues to mitosis
When and what happens at the mitosis checkpoint
During M phase, checks whether or not mitosis is complete, if so the cell divides and the cycle repeats
