Topic 2 - Replication Flashcards
What are the three key features of interphase?
- Cell growth: the cell increases in size and proteins and organelles are synthesised to support the division process.
- Replication: DNA replication occurs, ensuring each daughter cell will have an identical copy of genetic material and this result in the formation of sister chromatids which are joined at the centromere.
- Preparation for division: chromosomes begin to condense, becoming visible under the microscope in later stages of interphase and energy stores are increased to fuel south division (ATP).
What are the stages of interphase?
G1 phase: (first gap phase)
S phase: (synthesis phase)
G2 phase: (second gap phase)
Explain the G1 phase of interphase
- The cell grows and performs its normal functions
– Organelles such as mitochondria and ribosomes are replicated.
– The cell ensures it has sufficient nutrients and energy to proceed.
Explain the S phase of interphase.
– DNA is replicated producing identical copies for division.
– Each chromosome now consists of two sister chromatids
Explain the G2 phase of interphase
– The sell continues to grow and prepare for mitosis.
– Final checks are carried out to ensure there is no damage to DNA.
– Enzymes and proteins required for division are produced
What is the importance of interphase?
Insures the sellers promptly prepared for division and guarantees that genetic material is accurately replicated, reducing the risk of mutations.
What are the three key features of mitosis?
- Produces two identical daughter cells
– Each daughter cell has the same number of chromosomes as the parent cell (diploid).
– Ensures genetic consistency, meaning no genetic variation arises from mitosis
What happens during prophase?
– Chromosomes condensed, becoming visible as two sister chromatids join at the centromere
– The nuclear envelope breaks down
– Spindle fibres begin to form, extending from the centrioles
What happens during metaphase?
– Chromosomes lineup along the equator of the cell.
– Spindle fibres attached to the centromeres of each chromosome.
What happens in anaphase?
– The spindle fibres contract, pulling the sister chromatids apart.
– The chromatids are now individual chromosomes and are pulled to opposite poles of the cell.
What happens during telophase?
– Chromosomes arrive at the poles and decondense
– The nuclear envelope reforms around each set of chromosomes forming two nuclei.
– Spindle fibres disintegrate.
What happens with cytokinesis?
– The cytoplasm divides, producing two separate daughter cells.
What is the importance of mitosis?
Growth: increases the number of cells in an organism during development.
Repair: replaces damage or dead cells to maintain tissue health.
Asexual reproduction: produces offspring in some organisms.
Compare mitosis and meiosis
Growth, repair, asexual reproduction - production of gametes (sexual reproduction)
One division - two divisions
Two identical daughter cells produced - for genetically unique daughter cells produced
No genetic variation.- genetic variations due to crossing over and independent assortment.
How would you prepare sample for investigating plant root tips?
Use root tips as these contain actively dividing cells.
Cut the root tips (about 1-2 mm )from the growing end where mitosis occurs.
How would you fix the root tip to investigate mitosis?
Place the root tips in a fixative solution (acetic alcohol) to preserve the cells and prevent further division.
How would you stain a root tip to investigate mitosis?
Stain the root tips with a dye such as toluidine blue or acetic orcein, which binds to chromosomes and makes them visible under the microscope.
How would you soften the tissue of the root tip in a mitosis investigation?
Heat the root tip gently an acid to breakdown the cell walls and allow the cells to spread out more easily.
How would you mount the root tip in a cell mitosis investigation?
Place the stained root tip on a microscope slide.
Use mounted needle to gently squash the tissue spreading the cells into a single layer to observe individual nuclei and chromosome.
What is the calculation for mitotic index?
Undergoing mitosis/total cells x 100
What safety precaution should you use in root tip investigations?
– Wear gloves and safety goggles when handling stains and acids.
– Use care when cutting root tips and handling sharp objects e.g. needles and a scalpel.
When does uncontrolled cell division occur?
When normal regulatory processes in the cycle breakdown leading to excessive and unchecked cell proliferation this can result in the formation of tumours, some of which can become cancerous and spread to other parts of the body..
What are the key features of uncontrolled cell division?
- Regulation of the cell cycle.
- Genes involved in cell regulation.
How does regulation of the cell cycle affect uncontrolled cell division?
Normal cell division is controlled by checkpoint in the cell cycle which ensure that DNA is accurately replicated and damaged cells are repaired or destroyed.
– Uncontrolled cell division occurs when these checkpoints fail due to specific genes.
What genes involved in the cell cycle regulation may cause uncontrolled cell division?
Proto-oncogenes: promote cell division under normal conditions and mutation converts them into oncogenes, which cause uncontrolled cell division.
Tumour suppressor genes: inhibit cell division and trigger cell death in damaged cells. Mutation in these genes allows cells to divide uncontrollably.
What is a benign tumour?
- grow slowly and remain confined to their original location
- do not invade other tissues or spread to other parts of the body
- often encapsulated and easier to remove surgically.
What is a malignant tumour?
- Grow rapidly and invade surrounding tissues.
- Cells can break off and spread via the blood or lymphatic system.
- Malignant tumours are cancerous and more difficult to treat.
What are the causes of cancer?
- Genetic mutation: changes in DNA that affect Proto-oncogenes or tumour suppressor genes.
- Carcinogens: substances that increase the risk of cancer by causing DNA damage e.g. tobacco and UV radiation.
- Lifestyle factors: poor diet, lack of exercise and excessive alcohol consumption.
- Infections Certain viruses can cause cancer
What methods are there to treat cancer?
Chemotherapy: drugs to disrupt the cell cycle by preventing DNA replication and interfering with spindle formation during mitosis. Affect dividing cells including healthy cells which caused side-effects like hair loss.
Radiotherapy: uses radiation to damage DNA in cancer cells triggering cell death.
Surgery: remove tumours, often combined with chemotherapy or radiotherapy to kill remaining cancer cells.
