B9 Cell cycle Flashcards
Describe the steps in DNA replication.
- DNA helicase breaks hydrogen bonds
- Both strands act as templates
- Free DNA nucleotides align via complimentary base pairing
- DNA polymerase joins nucleotides via phosphodiester bonds
(condensation reaction) - New DNA double helix, one template is the original strand and one is the new strand (semi-conservative replication)
Describe binary fission in bacteria.
- Replication of plasmids and circular DNA
- Division of the cytoplasm to produce daughter cells
Describe the appearance and behaviour of chromosomes during mitosis.
(During prophase)
1. Chromosomes
coil / condense / shorten / thicken / become visible;
2. (Chromosomes) appear as (two sister) chromatids joined at the
centromere;
(During metaphase)
3. Chromosomes line up on the equator / centre of the cell;
4. (Chromosomes) attached to spindle fibres;
5. By their centromere;
(During anaphase)
6. The centromere splits / divides;
7. (Sister) chromatids / chromosomes are pulled to opposite poles /
ends of the cell / separate;
(During telophase)
8. Chromatids / chromosomes
uncoil / unwind / become longer / thinner.
What is cancer?
- Cells that have damaged DNA (mutations)
- Uncontrolled growth of cells which results in abnormal group of cells called tumours
What does cancer look like?
- Irregular shape cell
- Cells have more than one nucleus
- Different antigens on their surface
- Divide faster
What are the three stages of the cell cycle
- interphase
- Mitosis
- cell division (cytokinesis)
Describe the stages in the cell cycle.
- Interphase
- DNA replicates and cell grows in size
- Normal functions take place - Prophase
- DNA condenses into chromosomes
- Nuclear membrane breaks down
- Centrioles form spindle fibres - Metaphase
- Chromosomes line up in the centre
- Spindle fibres attach to centromere - Anaphase
- Spindle fibres contract
- Chromosomes split and centromeres divide - Telophase
- Nucleus reforms and chromosomes move to either ends
- Chromosomes uncoil into DNA strands - Cytokinesis
- Cell cytoplasm and cell membrane split
- Two genetically identical cells are formed
What is the definition of Oncogenes?
They code for proteins that stimulate division. If mutated, the proteins may over stimulate cell division
What is a Proto-oncogene?
They stimulate the cell cycle and if mutated, the cell cycle is continually active
What is the function of Tumour suppressor genes?
They code for a tumour suppressor protein which stops or slows the cell cycle, if this gene mutates it may lead to there being no way to slow mitosis, causing cancer
What does treatment for cancer cause in the cell cycle?
-Interfere with DNA replication and mitosis ( prevent spindle formation)
What normal cells are most commonly effected by chemotherapy?
- Blood cells in bone marrow
- Cells in mouth and stomach
- Hair follicles
What is the reason we use acid in the required practical with garlic cloves?
Breaks down cell walls to get more stain in
Why do we stain cells in the required practical?
To stain the chromosomes and make them visible
Why do we use root tips?
Cells are dividing here so you will see stages of mitosis
Why do the cells need to be squashed?
To provide a single layer of cells to allow light through
How do you work out the mitotic index?
number of cells in mitosis / total number of cells in view
