4. Cell division - Mitosis Flashcards
Describe the cell cycle.
In multicellular organisms the cells which keep their ability to divide follow a process called the cell cycle.
It starts when a cell has been produced by cell division and ends with the cell dividing to produce 2 identical cells.
Cell cycle = interphase and mitosis.
Describe what happens during interphase.
Cell carries out normal functions and preps for division.
Cell’s DNA is unravelled and replicated - doubles its genetic content.
Organelles replicate so it has spare one.
ATP content is increases - provides energy for cell division.
Describe what happens in mitosis.
A parent cell divides to produce 2 genetically identical daughter cells - contain an exact copy of DNA from parent cell.
Its needed for growth of mulitcellular organisms and repairing of damaged tissue.
Series of divisions - prophase, metaphase, anaphase and telophase.
What is the structure of chromosomes in mitosis?
As mitosis begins = chromosomes are made. of 2 strands joined in middle by centromere.
Separate strand = chromatids.
2 strands on same chromosome = sister chromatids.
2 strands because each chromosome already has made an identical; copy of itself during interphase.
When mitosis is over = chromatids end up as one-strand chromosomes in new daughter cell.
What happens in 1. prophase?
Chromosomes condensing - get shorter + fatter.
Tiny bundles of protein called centrioles start moving to opposite poles of cell - forming network of protein fibres called the spindle.
Nuclear envelop breaks down.
Chromosomes lie free in cytoplasm.
What happens in 2. metaphase?
Chromosomes - 2 chromatids line up along the middle of the cell and become attached to spindle by their centromere.
What happens in 3. anaphase?
Centromeres divide - separates each pair of sister chromatids.
Spindle contracts pulling chromatids to opposite poles of spindle - centromere first.
Chromatids appear v shaped.
What happens in 4. telophase?
Chromatids reach opposite poles of spindle.
Uncoil - become long + thin again called chromosome.
Nuclear envelope forms around each group of chromosomes - now they;re 2 nuclei.
Cytoplasm divides - 2 daughter cells that are genetically identical to original cell.
What is the term used to describe the dividing of the cytoplasm?
Cytokinesis.
What happens when mitosis has finished?
Each daughter cell starts interphase part of the cell cycle to get ready for next stage of mitosis.
How long does each stage in mitosis last?
The time taken for each stage of mitosis varies depending on the cell type and the environmental conditions.
What are mitosis and cell cycle controlled by?
Genes
What happens if there’s a mutation in a gene ?
It could alter cell division the cells could grow out of control as gene has been mutated / altered
This forms tumour - cancer is a tumour
What are mutations
Changes in base sequence
What is the aim of cancer treatments ?
To disrupt the cell cycle to control rate of cell division.
This kills tumour cells.
