Cell Cycle Flashcards
What are the two types of nuclear division?
Mitosis
Meiosis
What is chromatin?
More spread out form of DNA
What is a chromosome?
A mor condensed form of DNA
What’s a centromere?
Attaches two genetically identical molecules made from DNA replication
What is a centriole?
Small hollow cylinders which form centrosomes
What are centrosomes?
2 hollow cylinders orientated at right angles to one another and form a network of microtubules/filaments (spindle fibres)
What are the three main stages of the cell cycle?
Interphase
Mitosis
Cytokinesis
What are the three stages of interphase?
G1
S
G2
What happens during the G1 stage of interphase?
- Growth of cell
- Duplication of organelles
- Protein Synthesis
What happens during the S stage of interphase?
DNA replication
What happens during the G2 stage of interphase?
- More growth
- Checking for errors in replicated DNA
What are the 4 stages of Mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What happens during PROPHASE of mitosis?
- The nuclear envelope disintergrates
- The nucleolus disappears
- Chromatin condenses (shortens/thickens) to form chromosomes
- Centrioles move to opposite poles of the cell
- Spindle fibres (microtubules) start to develop
What happens during the METAPHASE stage of mitosis?
- Chromosomes line up along the equator (in the middle of the cell)
- Attached to the spindle fibres by their centromeres
What happens during the ANAPHASE stage of mitosis?
- Spindle fibres contract and shorten pulling sister chromatids apart and to opposite poles of the cell
- Centromeres divide in two separating each pair of sister chromatids
- This appears V-Shaped
What happens during the TELOPHASE stage of mitosis?
- Chromatids reach opposite poles on spindle fibres - called chromosomes
- Chromosomes decondenses to reform chromatin
- Spindle fibres disintegrate
- Nuclear envelope reforms around each group of chromosomes
- Nucleolus reappears
- Clevage furrows form to begin cytokinesis
What is a clevage furrow?
When the cell pinches together to perform cytokinesis
What is cytokinesis?
The cytoplasm splits/divides to form 2 genetically identical daughter cells
Why is only the root tip used when calculating a mitotic index?
- They have meristem cells at the root tip which are actively undergoing mitosis
- Cells further up from the root tip are elongating but not dividing
How do prokaryotic cells divide?
Binary Fiisoon
Describe the process of Binary Fission?
- Cell replicates it’s circular DNA and plasmids
- The cell elongates and grows separating the DNA loops to opposite ends of the cell
- Cross walls form so membrane invaginate (fold in) and the cytoplasm divides
- Forms two daughter cells
Why do we use Logs when working out bacteria cell growth ?
It helps us to compare data with a large range of values more accurately
What type of process is mitosis?
It’s a GENE CONTROLLED process
What are the two types of genes which control mitosis?
Oncogenes
Tumour Suppressor Genes
What do Proto - Oncogenes do when switched on?
Cause cell to divide
If the Proto - Oncogenes mutates to an Oncogene what happens?
The oncogene becomes permanently switched on leasing to uncontrolled cell division
What is a TS gene?
Tumour Suppressor gene
What is the function of TS genes?
Slows down cell division (helps maintain normal rates of cell division)
What will happen is a mutation of the TS gene occurs?
Leads to uncontrolled cell division and tumour growth
What are cancer treatments directed at?
Controlling the rate of cell division by killing rapidly dividing cells through blocking parts of the cell cycle
How does chemotherapy control rapidly dividing cells?
- Prevents DNA replication
- Inhibits metaphase by preventing spindle fibres forming
- Inhibits nucleotide synthesis
What is the problem with cancer treatments like chemotherapy?
It can interfere with with the cell cycle of normal cells which divide rapidly (causing damage)
For example hair producing cells = Hair loss
How do you calculate mitotic index?
Number of cells in mitosis (visible chromosomes) / total number of cells
