Theme 4- Module 1 (Mitosis) Flashcards
Why is cell division also considered reproduction in prokaryotic cells?
Bc the division of one prokaryotic cell will give rise to a new organism
What is binary fission?
The process of cell division (asexual reproduction) in prokaryotes
What is the first step of binary fission?
DNA of the bacterial chromosome is attached by proteins to the inside of the plasma membrane
True or false: in binary fission, newly synthesized DNA is also anchored to the plasma membrane
True
What’s the difference between stem cells in the adult body and stem cells in embryos?
Adult stem cells cannot give rise to all cell types in the organism
Only able to replace non-reproducing specialized cells (ie. mammalian adult skeletal muscle)
In what situation would stem cells replace mammalian adult skeletal muscle?
When the muscle is damaged
What are the stages in interphase (in order)?
G1 phase (growth)
S phase (synthesis)
G2 phase (growth)
What happens during the G1 phase?
Cell gets ready for synthesis
What happens during the S phase?
Replication of DNA
What happens during the G2 phase?
Cell gets ready for mitosis
Give examples of cells that req freq turnover
Epithelial cells of the intestine or the skin
Cells that make up the lenses of our eyes, nerve cells and even mature muscle cells enter into a permanent ____ phase
G0
When does the G0 phase occur?
Somewhere between the M and S phase
In what phase are the quiescent satellite stem cells in?
The G0 phase
What are the five distinct stages of mitosis based/characterized on?
Morphometrically characterized based on the distinctive changes that occur to the chromosomes (position and features)
Who discovered that distinct stages of mitosis could be staged based on chromosomal position and features?
Walther Flemming
Describe Walther Flemming’s work
Analyzed developing salamander embryos that he had stained to be able to visualize the chromosomes
What are the five phases of mitosis?
Prophase Prometaphase Metaphase Anaphase Telophase
What are the main goals of interphase?
To duplicate and condense the chromosomes of cells
(to allow for the daughter cells to acquire the the same amount of genetic information as the parent cell in a relatively short period of time)
What allows for tight compaction of the chromosomes?
Association with histones and other proteins
True or false: the centromeres of the chromosomes do not get replicated
False
The centromere is fully replicated, it is simply so highly compacted that the paired centromeres appear fused together
How many chromosome pairs do we have?
23
How many homologous pairs of chromosomes do we have?
22
How many sex chromosomes do we have?
1 pair (two in total)
True or false: cytokinesis is the same in both plants and animals
False
Plants have a cell wall, so they need to account for that. They lay down a newly developed cell wall along a cell plate region in the middle of the dividing cell. Once the forming cell wall fuses with the original cell wall, cytokinesis is then complete.
Describe Tim Hunt’s experiment and results
He decided to measure the protein level changes of dividing sea urchin embryos
Procedure: Hunt added radioactively labelled methionine to the sea urchin eggs. He took samples of the rapidly dividing embryos every 10 minutes and visualized any changes in protein levels using gel electrophoresis.
Results:
- most protein bands on the gel became darker as cell division and embryonic development progressed
- one protein oscillated; increased then decreased with each subsequent cell division. Called this protein cyclin
What is gel electrophoresis?
A procedure that allows for distinct separation of different protein types
What does the mitosis promoting factor do?
Allows for the transition from the G2 to M phase of the cell cycle; plays a regulatory role on cell cycle progression
What does the mitosis promoting factor consist of?
A cyclin protein + a cyclin- dependent kinase (or CDK) protein
What are kinases and what do they do?
They are enzymes that activate or inactivate other proteins by phosphorylating key amino acids on the target proteins
Why have the kinases that regulate the cell cycle acquired the name “cyclin-dependent kinases”?
Bc for much of the time they are in an inactive form until they are activated by binding to cyclin proteins
What does the activity of cyclin-dependent kinases depend on?
The changes in the concentration of its activating cyclin protein
True or false: the conc of cyclin does not change
False
It can change
True or false: the conc of cyclin-dependent kinases does not change
True
The conc doesn’t change; just the number of them that are active
True or false: the conc of cyclin DECREASES as the embryo divides by mitosis
True
What are the different types of cyclin-CDK complexes that are involved in the regulation of each stage of the cell cycle?
G1/S cyclin-CDK complex
S-cyclin-CDK complex
M cyclin- CDK complex
What does the G1/S cyclin-CDK complex do?
Helps to prepare the cell for DNA replication (such as increasing the expression of histone proteins)
Needed for the transition from the G1 to S phase
What does the S-cyclin-CDK complex do?
Helps to initiate DNA synthesis
What does the M cyclin- CDK complex do?
Initiates the process of mitosis
How do CDK complexes help initiate mitosis?
Phosphorylate structural proteins that are needed for:
- nuclear membrane breakdown
- regulation of the assembly of microtubules in the mitotic spindles
What is the purpose of cell cycle checkpoints?
Able to block cyclin-CDK activity should something go wrong during the progression of the cell cycle
- can pause cell division until the preparation for the next stage of the cell cycle is complete
- an opportunity for damage to be repaired
What are the three major checkpoints of the cell cycle and when do they occur?
DNA damage checkpoint at the end of G1 phase
DNA replication checkpoint at the end of the G2 phase
Spindle assembly checkpoint before anaphase during mitosis
What is required in order for each cell to pass the G1 checkpoint (and enter S phase for replication)?
Undamaged DNA
What is required in order for each cell to pass the G2 checkpoint (and enter mitosis phase)?
All DNA has to be replicated
What is required in order for each cell to pass the M checkpoint (and complete mitosis)?
All chromosomes have to be attached to a microtubule from the mitotic spindle
