Mitosis Flashcards
(39 cards)
What type of cells are produced by mitosis?
Genetically identical daughter cells.
State three biological roles of mitosis in organisms.
• Growth of multicellular organisms.
• Repair of damaged tissues.
• Asexual reproduction in some organisms.
What is the cell cycle?
The cell cycle is the series of stages that cells go through to grow and divide.
Name the longest phase of the cell cycle and what it involves.
The longest phase of the cell cycle is Interphase – Longest phase, involves cell growth & DNA replication.
Describe the events that occur during each stage of interphase.
• G₁ (Gap phase 1): Cell grows, makes proteins & organelles.
• S (Synthesis): DNA replication → chromosomes become 2 sister chromatids.
• G₂ (Gap phase 2): Cell grows more, produces proteins for division.
List three key processes that occur during interphase.
• DNA unravels & replicates.
• Organelles replicate.
• ATP content increases.
When does mitosis occur in the cell cycle?
Mitosis occurs after interphase.
What is the result of mitosis?
Results in two genetically identical daughter cells.
Describe the key events in prophase.
• Chromosomes condense (shorter, fatter).
• Centrioles move to poles and form spindle fibres.
• Nuclear envelope breaks down.
• Chromosomes lie free in cytoplasm.
What happens during metaphase?
• Chromosomes (each with 2 chromatids) align at cell equator.
• Attach to spindle fibres by centromeres.
Explain what happens during anaphase.
• Centromeres divide, separating sister chromatids.
• Spindle fibres pull chromatids to opposite poles (centromere first).
• Chromatids look V-shaped.
Describe the events that occur in telophase.
• Chromatids uncoil and form chromosomes again.
• New nuclear envelopes reforms around each group of chromosomes .
• Cytoplasm divides (cytokinesis) and 2 identical daughter cells are produced
What information is needed to calculate how long a stage of mitosis lasts?
• Number of cells in a stage
• Total cells observed
• Duration of the cell cycle
Write the formula used to calculate the time spent in one stage of mitosis.
Time in stage = (cells in stage / total cells) × duration of cell cycle
What regulates mitosis?
Mitosis is regulated by genes.
How can cancer form as a result of problems in the cell cycle?
Cancer can form due to
•Mutation in these genes resulting to uncontrolled division causing tumours.
•If tumour invades surrounding tissue its is cancer.
How do cancer treatments target the cell cycle?
Treatments disrupt the cycle that rapidly divides cells (e.g. tumour cells).
How do G₁ phase inhibitors work?
G₁ phase inhibitors Prevent enzyme synthesis needed for DNA replication therefore cell cannot enter S phase and dies
How do S phase inhibitors work?
S phase inhibitors Damage DNA which triggers cell death if damage is detected at checkpoints.
Why might normal cells also be affected by these treatments?
Normal dividing cells can be affected too.
Why is the tip of the root used in the mitosis practical?
Because the tip of the root is where growth occurs (and so that’s where mitosis takes place).
List the full method used to prepare a root tip for viewing mitosis.
- Cut 1 cm of root tip (onion).
- Fix in ethanoic acid (if staining with ethano-orcein).
- Place in 1 M HCl at 60°C for 5 mins.
- Rinse in cold water & dry.
- Cut 2 mm of tip; discard the rest.
- Use needle to break open and spread cells.
- Add stain (e.g. toluidine blue, orcein, Feulgen).
- Add cover slip and squash straight down (don’t smear).
- Observe under optical microscope.
Describe how to observe prepared cells under a microscope.
- Clip slide to microscope stage.
- Use low-power objective lens.
- Use coarse adjustment to bring stage close.
- Look through eyepiece, lower stage slowly to focus.
- Use fine adjustment to sharpen image.
- Switch to high-power lens if needed, refocus.
- Label any drawings, state magnification.
What is the mitotic index used for?
Mitotic index is used to assess the rate of cell growth or detect abnormal tissue (e.g. cancer).
