Topic 5 - The Mitotic Cell Cycle Flashcards
How long is DNA
2nm
What is the Centromere
Holds the two chromatids together. There are not genes in this region. It is the region that becomes attached to the spindle fibres in divison
What do telomeres do
They prevent parts of genes being lost after DNA replication and stop uncontrolled cell division.
Why are telomeres important
Because they prevent uncontrolled cell division, which can lead to tumors which can be cancerous
What are Chromatids [2]
They contain 1 DNA molecule, which is composed of genes.
They are held together by a centromere formed during interphase.
What is a centrosome
An organelle made up of two centrioles, near the nucleus in animal cells and is involved in the formation of the spindle prior to nuclear divison.
What is chromatin [3]
A material containing protein,
it is present in the nucleus of eukaryotic cells at interphase,
and turns into DNA
When are chromosomes visible
When stained during nuclear division
What are sister chromatids
Either of the two identical chromatids formed by the replication of a chromosome
What are the components that make up a chromosome [5]
- DNA
- Histone Protein
- Sister chromatids
- Centromere
- Telomeres
What is the purpose of Mitosis [3]
Produces 2 genetically identical daughter cells for:
- Growth
- Cell Replacement
- Asexual reproduction
What is the cell cycle
Regulated cycle of cell division with intermediate periods of growth
Outline the stages of the cell cycle
- Interphase
- Mitosis
- Cytokinesis
Outline what happens during interphase [3]
• G1 - Cell synthesises proteins for replication (e.g. tubulin for spindle fibres), cell size doubles
• S - DNA replicates, chromosomes consist of two sister chromatids joined at a centromere
• G2 - Organelles divide
What are the 4 stages of mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
Outline what happens in prophase [3]
- Chromosomes condense and become visible X shaped, two sister chromatids joined at centromere
- Centrioles move to opposite poles of the cell and mitotic spindle fibres form
- Nuclear envelope and nucleolus break down, leaving chromosomes free in the cytoplasm
Outline what happens during metaphase
Sister chromatids line up at the cell equator attached to the mitotic spindle by their centromeres
Outline what happens during anaphase [3]
- Spindle fibres contract, centromeres divide
- Sister chromatids separate into two distinct chromosomes and are pulled to opposite poles of the cell (looks like V shape)
- Spindle fibres break down
What does anaphase require to happen
ATP from hydrolysis
Outline what happens during telophase [3]
- Chromosomes decondense and can no longer be observed
- New nuclear envelopes form around each set of chromosomes - two new nuclei each with one copy of each chromosome
- Cytoplasm constricts
What happens during cytokinesis [2]
- Cell membrane cleavage furrow forms
- Contractile division of cytoplasm
What are stem cells
Cells that are unspecialised and retain the ability to differentiate into a range of cell types
What are the 4 types of stem cell
- Totipotent
- Pluripotent
- Multipotent
- Unipotent
What are totipotent stem cells
can develop into any cell type including the placenta and embryo
What are Pluripotent stem cells
can develop into any cell type excluding the placenta and embryo
What are multipotent stem cells
can only develop into a few different cell types
What are unipotent stem cells
can only develop into one type of cell
What are 2 uses of stem cells
- Repair of damaged tissue
- Drug testing on artificially grown tissues.
Why is regulation of the cell cycle important
Irregular growth of cells where repair is not required can result in the formation of cell masses, which can lead to cancer
What are telomeres [2]
- Multiple repeat units of short sequence DNA that cap chromosome tips.
- The DNA that makes up telomeres is rich in guanine and cytosine
State the role of telomeres [3]
- prevent the progressive loss of DNA in replication
- the enzyme responsible for the replication cannot replicate the full length of the chain
- Telomeres provide protection against any loss of coding DNA
Where can stem cells be found in adult humans? [5]
- bone marrow
- skin
- gut
- heart
- brain
Uses of stem cells [4]
- repair of damaged tissue after myocardial infarction
- drug testing on artificially grown tissues
- treating neurological diseases
- researching developmental biology
