Cells: Cell cycle and mitosis Flashcards
(28 cards)
Name the three MAIN stages in the cell cycle
- Interphase
- Mitosis
- Cytokinesis
Name the three stages of interphase
- G1 phase
- S phase
- G2 phase
What occurs during the G1 phase
Cell is growing then receives a signal to divide
What occurs during the S phase
DNA replicates
What occurs during the G2 phase
- Synthesis of various proteins occurs (ribosomes, microtubules)
- Checkpoint where DNA is proof-read
How many chromosomes do humans have in their body cells
46
Name and describe the features of a chromosome
Centromere - region where the cells’ spindle fibres attach (centre of the chromosome)
Chromatid - one of the two identical halves of a chromosome
Sister chromatids - Identical copies of a single chromosome
What is mitosis
- The process of nuclear division by which two genetically identical daughter nuclei are produced that are also genetically identical to the parent cell nucleus
Name the stages of mitosis in order
- Prophase
- Metaphase
- Anaphase
- Telophase
Name all the stages in the cell cycle in order
- Interphase (G1, S , G2)
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
State the main events of each stage of mitosis
- Prophase - Chromosomes condense
- Metaphase - Chromosomes line up in them middle of the cell
- Anaphase - Chromatids break apart at he centromere and move to opposite poles
- Telophase - Two nuclei form after nuclear envelopes reform around each group of chromosomes
What happens during prophase
- Chromosomes condense and are now visible when stained
- The two centrosomes (replicated in the G2 phase just before prophase) move towards opposite poles of the cell
- Spindle fibres begin to emerge from the centrosomes
- The nuclear envelope (nuclear membrane) breaks down into small vesicles
What happens during metaphase
- Centrosomes reach opposite poles
- Spindle fibres continue to extend from centrosomes
- Chromosomes line up at the equator of the spindle
- Spindle fibres reach the chromosomes and attach to the centromeres
- Each sister chromatid is attached to a spindle fibre
What happens during anaphase
- The sister chromatids separate at the centromere
- Spindle fibres begin to shorten
- The separated sister chromatids are pulled to opposite poles by the spindle fibres
What happens during Telophase
- Chromosomes arrive at opposite poles and begin to decondense
- Nuclear envelopes begin to reform around each set of chromosomes
- The spindle fibres break down
What happens during cytokinesis in animal cells
A cleavage furrow forms and separates the daughter cells
What happens during cytokinesis in plant cells
- A ‘cell plate’ forms at the site of the metaphase plate
- Once the cell plate reaches the cell walls of the parent cell, new cell walls are produced, separating the new daughter cells
Why is mitosis needed
To grow and repair body cells
What occurs during interphase
- Cell receives a signal to divide
- DNA replicates
- Synthesis of various proteins occurs (ribosomes, microtubules)
- Checkpoint where DNA is proof-read
- ATP content increases
How are tumours formed
When cells develop mutations that make them divide uncontrollably
How can a cancer treatment target the cell cycle
- G1 (cell growth and protein production): Some chemical drugs (chemotherapy) prevent the synthesis of enzymes needed for DNA replication
- If these aren’t produced, the cell is unable to enter the synthesis phase (S), disrupting the cell cycle and forcing the cell to kill itself
- S phase (DNA replication): Radiation and some drugs damage DNA. At several points in the cell cycle (including just before and during S phase) the DNA in the cell is checked for damage
– If severe damage is detected, the cell will kill itself, preventing further tumour growth
State the main event that occurs during prophase
Chromosomes condense
State the main event that occurs during metaphase
Chromosomes line up in them middle of the cell
State the main event that occurs during anaphase
Chromatids break apart at he centromere and move to opposite poles
