Unit 11 – Assignment 2
Cell Division
- Different stages of mitosis and meiosis
- Experimenting lily anther and onion tip
- Define magnification used on microscope to determine stages.
- Structure and function of chromosomes and then variations.
A chromosome contains genetic information including DNA and proteins found in the nucleus. Genes
are copied into the new cells when cells are divided, and they are responsible for the characteristics
of an organism. Located on chromosomes, they entail very tightly and long coiled molecules of DNA.
In a eukaryotic cell, nucleosomes are formed when the DNA double helix is wrapped around the
histone and then they are coiled to form chromatins. Which are organised into chromosomes. Large
amounts are easily stored in small spaces due to DNA being compact.
Before a cell divides, chromosomes are thin and long strands until after they become more visible as
they are shorter and thicker. Caused by condensation. When a chromosome is duplicated into two
strands, they are known as chromatids (which are genetically identical) and are joined at the
centromere. As shown.
Centromere – structure that holds
the chromatids.
Chromatids – genetically identical
Autosomes – any of the 1-22
homologous.
Telomere
Types of chromosomes
Homologous – known as a group of chromosomes, and in every pair, one is inherited from the
mother and the other from the father. An example is humans having 46 chromosomes and is known
as the diploid number of humans.
Autosomes and Sex chromosomes – Now autosomes are any of the 22 pairs, however, do not
determine the sex. Sex chromosomes form homologous pairs in only females. The Y chromosomes
are much smaller than the X chromosome and do have some identical material.
Karyotyping is the process of identifying chromosomes through staining. Before the process
undergoes mitosis chromosomes become visible. Cells which divide quickly are put into water
causing them to burst as water is taken in by osmosis. Rooting the nuclear membrane rupturing and
chromosomes to be released. Viewed by a light microscope after being stained.
Chromosomes to be cut and arranged in homologous pairs using banding pattern and sizes. Can be
used to diagnose chromosome abnormalities, i.e. Edwards syndrome or Down syndrome.
, Cell Cycle is mostly associated with cells which are dividing, whether that’s somatic cells or cells to
produce gametes. The stages consist of G1, S, G2, Mitosis and Cytokinesis. As shown below.
G0 – This resting phase is triggered earlier during G1 by a
checkpoint chemical. The normal process is followed however
it’s not actively dividing. Cells such as neurons remain in this
phase and some cell types don’t have this phase. They can
also undergo senescence or even programmed death.
G1 – Growth phase which is regulated by the p53 tumour
suppressor gene. Organelles then duplicate, RNA is
transcribed, and protein synthesis occurs to create enzymes.
It is then checked before moving onto S.
S – Synthesis phase is where the DNA is replicated into 4
copies of each chromosome. Occurs quickly as DNA is
exposed to mutagenic agents. Also, the point of no return.
G2 – Growth phase 2 is more cell growth and the cyclin-CDK complexes and restores proteins which
are required to condense chromosomes and making the spindle. Ensuring and preparing for mitosis.
Mitosis – Explained in more detail below. In between G2 and M a checkpoint ensures DNA is
replicated properly and any faults have been found and rectified. Chromatin condenses allowing the
cell to enter mitosis or nuclear division. Another checkpoint occurs during metaphase to ensure the
cell is ready to finish mitosis. - Cytokinesis follows.
A centriole is a microtubule-organisation centre and is made from proteins known as tubulin. Mainly found in pairs
and are duplicated during S phase. Microtubules are organised into the spindle when a pair migrates to the opposite
side of the cell. Centrioles are found in animal cells, not usually in plant cells.
Checkpoints are required to stop uncontrolled cell division leading to tumours. It also senses defects
and repairs damage to DNA. Carefully controls what order cell cycle occurs in and ensures it can’t be
reversed and is only copied once per cycle.
Proto-oncogene produces proteins which regulate cell division, differentiation, and growth. An
example is p53, when a mutation happens in this gene, cell division isn’t regulated forming a
tumour. Cancer treatments are used to disturb the different stages if cell cycle which can interfere
with either protein synthesis or DNA replication.
Mitosis is where nuclear division takes place and produces genetically identical cells used to repair,
grow, or replace dead cells. The stages are prophase, metaphase, anaphase, and telophase. The two
stages before and after this are interphase and cytokinesis and aren’t included in the mitosis
process. Each are explained and shown in more detail below.
Before mitosis comes interphase. In this stage processes such as
respiration and protein synthesis occur as cells are not dividing. DNA is
replicated and energy is stored preparing for division. This isn’t a resting phase.
The first stage in prophase (present) where chromosomes are visible
(condensed), and centrioles are moved to opposite poles of the cell causing the
nuclear membrane and nucleolus to disappear forming the spindle fibres.
Next is metaphase (middle) where chromosomes are to be lined up in the
centre of the cell where spindle fibres attach to the centromeres.
Thirdly comes anaphase (apart) when the centromere is split, and
chromosomes begin to move to opposite poles of the cell.
Lastly is telophase (two) when two new nuclear membranes are formed and
each of the nucleus entails the exact same chromosome and nucleolus forms.
After mitosis is cytokinesis where cell membranes are split into two identical
daughter cells.
Cell Division
- Different stages of mitosis and meiosis
- Experimenting lily anther and onion tip
- Define magnification used on microscope to determine stages.
- Structure and function of chromosomes and then variations.
A chromosome contains genetic information including DNA and proteins found in the nucleus. Genes
are copied into the new cells when cells are divided, and they are responsible for the characteristics
of an organism. Located on chromosomes, they entail very tightly and long coiled molecules of DNA.
In a eukaryotic cell, nucleosomes are formed when the DNA double helix is wrapped around the
histone and then they are coiled to form chromatins. Which are organised into chromosomes. Large
amounts are easily stored in small spaces due to DNA being compact.
Before a cell divides, chromosomes are thin and long strands until after they become more visible as
they are shorter and thicker. Caused by condensation. When a chromosome is duplicated into two
strands, they are known as chromatids (which are genetically identical) and are joined at the
centromere. As shown.
Centromere – structure that holds
the chromatids.
Chromatids – genetically identical
Autosomes – any of the 1-22
homologous.
Telomere
Types of chromosomes
Homologous – known as a group of chromosomes, and in every pair, one is inherited from the
mother and the other from the father. An example is humans having 46 chromosomes and is known
as the diploid number of humans.
Autosomes and Sex chromosomes – Now autosomes are any of the 22 pairs, however, do not
determine the sex. Sex chromosomes form homologous pairs in only females. The Y chromosomes
are much smaller than the X chromosome and do have some identical material.
Karyotyping is the process of identifying chromosomes through staining. Before the process
undergoes mitosis chromosomes become visible. Cells which divide quickly are put into water
causing them to burst as water is taken in by osmosis. Rooting the nuclear membrane rupturing and
chromosomes to be released. Viewed by a light microscope after being stained.
Chromosomes to be cut and arranged in homologous pairs using banding pattern and sizes. Can be
used to diagnose chromosome abnormalities, i.e. Edwards syndrome or Down syndrome.
, Cell Cycle is mostly associated with cells which are dividing, whether that’s somatic cells or cells to
produce gametes. The stages consist of G1, S, G2, Mitosis and Cytokinesis. As shown below.
G0 – This resting phase is triggered earlier during G1 by a
checkpoint chemical. The normal process is followed however
it’s not actively dividing. Cells such as neurons remain in this
phase and some cell types don’t have this phase. They can
also undergo senescence or even programmed death.
G1 – Growth phase which is regulated by the p53 tumour
suppressor gene. Organelles then duplicate, RNA is
transcribed, and protein synthesis occurs to create enzymes.
It is then checked before moving onto S.
S – Synthesis phase is where the DNA is replicated into 4
copies of each chromosome. Occurs quickly as DNA is
exposed to mutagenic agents. Also, the point of no return.
G2 – Growth phase 2 is more cell growth and the cyclin-CDK complexes and restores proteins which
are required to condense chromosomes and making the spindle. Ensuring and preparing for mitosis.
Mitosis – Explained in more detail below. In between G2 and M a checkpoint ensures DNA is
replicated properly and any faults have been found and rectified. Chromatin condenses allowing the
cell to enter mitosis or nuclear division. Another checkpoint occurs during metaphase to ensure the
cell is ready to finish mitosis. - Cytokinesis follows.
A centriole is a microtubule-organisation centre and is made from proteins known as tubulin. Mainly found in pairs
and are duplicated during S phase. Microtubules are organised into the spindle when a pair migrates to the opposite
side of the cell. Centrioles are found in animal cells, not usually in plant cells.
Checkpoints are required to stop uncontrolled cell division leading to tumours. It also senses defects
and repairs damage to DNA. Carefully controls what order cell cycle occurs in and ensures it can’t be
reversed and is only copied once per cycle.
Proto-oncogene produces proteins which regulate cell division, differentiation, and growth. An
example is p53, when a mutation happens in this gene, cell division isn’t regulated forming a
tumour. Cancer treatments are used to disturb the different stages if cell cycle which can interfere
with either protein synthesis or DNA replication.
Mitosis is where nuclear division takes place and produces genetically identical cells used to repair,
grow, or replace dead cells. The stages are prophase, metaphase, anaphase, and telophase. The two
stages before and after this are interphase and cytokinesis and aren’t included in the mitosis
process. Each are explained and shown in more detail below.
Before mitosis comes interphase. In this stage processes such as
respiration and protein synthesis occur as cells are not dividing. DNA is
replicated and energy is stored preparing for division. This isn’t a resting phase.
The first stage in prophase (present) where chromosomes are visible
(condensed), and centrioles are moved to opposite poles of the cell causing the
nuclear membrane and nucleolus to disappear forming the spindle fibres.
Next is metaphase (middle) where chromosomes are to be lined up in the
centre of the cell where spindle fibres attach to the centromeres.
Thirdly comes anaphase (apart) when the centromere is split, and
chromosomes begin to move to opposite poles of the cell.
Lastly is telophase (two) when two new nuclear membranes are formed and
each of the nucleus entails the exact same chromosome and nucleolus forms.
After mitosis is cytokinesis where cell membranes are split into two identical
daughter cells.
