Cell Division /Cell Cycle Flashcards
types of cell division
mitosis (one cell splitting into two cells)
meiosis
what is mitosis part of
Mitosis is part of a much longer process called the cell cycle
What does duration of cell cycle depend on
cell cycle can take a long time (duration of cell cycle depends on type of cell)
Is it possible for some cells to exit the cell cycle
Some cells can exit the cell cycle, either temporarily or permanently
General Stages of cell cycle - NAMES.
M (mitotic) phase - when mitosis takes place and cell divides into two
M phase relatively short period within whole cell cycle
Most of cell cycle is called interphase - cell may appear to be relatively inactive but lots of different processes are happening
During interphase, the cell is also carrying out the functions of that particular cell type e.g. intestinal epithelial cells are absorbing nutrients from the small intestine
Interphase can be divided into three phases - G1, S, G2 phase
Stages of interphase (in cell cycle) - G1. describe what happens
The first stage is called the G1 phase. During the G1 phase, the cell replicates organelles such as mitochondria
Replicating organelles requires a lot of proteins. So during G1, a high level of transcription and translation takes place
During G1 phase the size of the cell also increases. This ensures that when the cell divides, the two daughter cells are the correct size
explain why it is important for the cell size to increase during the G1 phase
During G1 phase the size of the cell also increases. This ensures that when the cell divides, the two daughter cells are the correct size
explain why lots of translation and transcription occurs in G1 phase
The first stage is called the G1 phase. During the G1 phase, the cell replicates organelles such as mitochondria
Replicating organelles requires a lot of proteins. So during G1, a high level of transcription and translation takes place
Stages of interphase (in cell cycle) - S. Describe what happens
After G1 (next), the cell passes into the S (Synthesis) stage.
During the S phase, all of the chromosomes are replicated
To do this, the cell needs to synthesise a lot/large amount of DNA.
Lots of DNA synthesis occurs
explain why lots of DNA synthesis occurs in S phase of Interphase
During the S phase, all of the chromosomes are replicated
To do this, the cell needs to synthesise a lot/large amount of DNA.
Lots of DNA synthesis occurs
Describe what happens in G2 (INTERPHASE IN CELL CYCLE)
Now the cell enters the G2 phase.
During G2, the cell replaces the energy stores used during the S phase. (energy stores increase)
The cell also continues to carry out transcription and translation
If any of the chromosomes have been damaged, then they are repaired during G2
Just like in the G1 phase, the cell continues to grow (size of cell increases)
What happens when cell finishes G2 stage
Once the cell has finished the G2 phase, it now enters the M (Mitotic phase)
The mitotic phase can be divided into two parts. / cell carries out two processes in mitotic phase. These are:
The mitotic phase can be divided into two parts:
In mitotic phase cell carries out two processes
Mitosis (where chromosomes separate into two nuclei)
The first part is called mitosis
during mitosis - chromosomes are separated into two nuclei
nucleus divides into two daughter nuclei
second part cytokinesis
during cytokinesis - cell divides into two
Cytokinesis (cell divides into two)
cell divides into two daughter cells each with a nucleus
What phase is the cell in if it exits the cell cycle
Sometimes cells can exit the cell cycle.
If this happens, then it is said that the cell is in the G0 phase
Reasons why cells enter G0. (subscript 0)
Fully differentiated cells enter G0 and stay there for the rest of their lives. For example neurons in adults (once reached maturity, fully differentiated, they never need to divide again) - also cardiac cells
Over time, the DNA in cells can be damaged. At a certain point the cell will no longer be able to divide. These cells are called Senescent cells
At this stage, the cell enters G0 permanently
Some cells enter G0 temporarily e.g. B memory cells
These cells can then be triggered to re-enter the cell cycle during an infection
Explain how the cell cycle is very tightly regulated
The cell cycle is very tightly regulated
At certain key points in the cell cycle, the cell checks that the cell cycle should continue
These are called checkpoints.
At any point, if a cell fails a check point, it will leave the cell cycle and enter G0.
How many checkpoints are there. Describe them
There are three check points.
Before the S phase, the cell must pass through the G1 checkpoint.
Here the cell checks that it has grown to the correct size. Also checks for DNA damage
If the cell satisfies the G1 checkpoint, then it passes into the S phase and carries out DNA replication
The next check pint is at the end of G2 before cell passes into the Mitotic phase.
At G2 checkpoint, the cell checks for DNA damage and cell has grown to the correct size
If this checkpoint is passed, then the cell moves into the Mitotic phase
The final checkpoint is called the metaphase checkpoint or spindle checkpoint
This checks that the chromosomes are assembled correctly n the mitotic spindle.
If this is the case/passes this checkpoint, then the cell completes mitosis and proceeds through cytokinesis
Draw a diagram showing the cell cycle
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTmyvL26jtcYAReJ9GcYNdGFlBiMVVkMWM_Qg&s
what are diploid cells
Cells which contain chromosomes in pairs
in most organisms including humans, what type of cell are virtually all of the cell
In most organisms, including humans, virtually all of the cells are diploid
in cell division by mitosis we start with ______ diploid cell and end up with _____ _______ diploid cells
in cell division by mitosis we start with ONE diploid cell and end up with TWO IDENTICAL diploid cells
describe the roles of mitosis in living organisms / purpose of mitosis
Cell division by mitosis takes place when we want identical copies of a cell e.g. when an organism grows or repairs itself
Used for asexual reproduction
division of nucleus is called ______
division of cell is called _____
division of nucleus is called mitosis
division of the cell is called cytokinesis
when do both mitosis and cytokinesis occur
Both mitosis and cytokinesis occur/take place during the M phase of the cell cycle
what cannot be seen during interphase, what can be seen instead?
During interphase, chromosomes cannot be seen in the nucleus.
The chromosomes are there, but they are not visible as distinct structures.
Instead this dark material can be seen, which is called chromatin
describe the structure of chromatin
what does the structure of chromatin allow for.
In chromatin, the chromosomes have a loose open structure
This means that the DNA is accessible for transcription and translation (replication)
what is a chromosome
A chromosome is a single long molecule of DNA
draw a diagram showing how chromosomes are replicated during interphase
https://images.nagwa.com/figures/explainers/650191397968/16.svg
—–> = DNA replication during interphase
what happens when chromosomes are replicated during interphase
When chromosomes are replicated during interphase, there is now (we now have) two identical molecules of DNA
These are called sister chromatids - they are identical
The point where the sister chromatids are joined is called the centromere
what is each chromosome in the chromosome pair called - when DNA replication during interphase has occured
each chromosome in the chromosome pair is called sister chromatids
what is the centromere
The point where the sister chromatids are joined is called the centromere
https://images.nagwa.com/figures/explainers/650191397968/16.svg
—–> = DNA replication during interphase
how often does DNA replication occur
The process of DNA replication during interphase happens for every chromosome - happens for each of 46 chromosomes (23 pairs) in humans
when does DNA replication take place, what is special about the chromosomes
DNA replication takes place during interphase
Chromosomes are not visible as distinct structures at this stage
