The Cell Cycle & Apoptosis Flashcards
What are the four coordinated processes involved in eukaryotic cell cycles?
- cell growth
- DNA replication
- distribution of the duplicated chromosomes to daughter cells
- cell division
What does mitosis (the M phase) involve?
Nuclear division and the separation of daughter chromosomes, usually ending with cell division.
What is cytokinesis?
The actual division of a cell following mitosis
What is interphase?
The period between mitoses when the chromosomes are decondensed and distributed throughout the nucleus
What happens in the G1 phase?
cell growth and making proteins for DNA replication
What happens during the S phase?
DNA replication and DNA synthesis
What happens during the G2 phase?
proteins for mitosis are made
What can reactivate cell division?
appropriate extracellular signals such as growth factors
What happens in the G0 stage?
cells remain metabolically active but no longer proliferate
What is the progression of cells through the cell cycle regulated by?
Extracellular signals from the environment and internal signals that monitor and coordinate the various processes that take place during different cell cycle phases.
What are the 2 questions that the cell is faced with before initiating mitosis and cell division?
Should I divide?
Am I capable of dividing properly?
What is the decision point in late G1 phase called in yeast cells? In animal cells?
“START” in yeast cells and the restriction site in animal cells
What are the factors determining the “START” point in yeast cells?
available nutrients, size, and mating factors
What are the factors determining the restriction site in animal cells?
extracellular growth factors
What happens when a cell passes the first decision point?
It is committed to proceed through S phase and the rest of the cell cycle (even if external factors such as growth factors are no longer present)
What are the four cell cycle checkpoints that control the “am I capable of dividing properly?” question?
- G1: ensures damaged DNA is repaired before being replicated in S phase
- S: continues monitoring DNA integrity
- G2: prevents initiation of mitosis if DNA is not completely replicated/is damaged
- M (spindle assembly checkpoint): inhibits spindle assembly if chromosomes aren’t distributed accurately to daughter cells
What happens if there is a problem at any of the 4 cell cycle checkpoints?
Cell cycle arrest will occur
What is the cell cycle of all eukaryotes controlled by?
A conserved set of protein kinases, which are responsible for triggering the major cell cycle transitions
What are cyclins?
proteins which regulate the activity of the enzymes which regulate the cell cycle
What are cyclin dependent protein kinases (Cdks)?
phosphorylating enzymes that are regulated by cyclins
What is the interaction of cyclins with Cdks responsible for?
triggering the major cell cycle transitions and for the progression of the cell cycle through its major checkpoints
What were the 3 model organisms used to identify the key molecules responsible for cell cycle regulation?
- frog oocytes
- yeast
- sea urchins
What was discovered through the study of frog oocytes?
Identified the maturation promoting factor (MPF)
What is the purpose of MPF?
MPF is a general regulator of the transition from G2 phase to M phase
What was discovered through the study of yeast?
Mutations in genes called cell division cycle mutants (cdcs) caused various cell cycle arrests, and these genes were found to encode for protein kinases.