Cell Division Flashcards
What are the stages in Mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What happens in the G1 (Growth Phase 1) of the cell cycle?
The cell grows.
Increase in the number of organelles
Proteins are made.
ATP synthesised
What happens in the G2 (Growth Phase 2) of the cell cycle?
The cell keeps growing.
Proteins are made.
ATP synthesised
What happens during the Synthesis phase?
Synthesis of the DNA (replication)
What is the order of the phases in the cell cycle?
G1 (Growth Phase 1) > Synthesis > G2 (Growth Phase 2) > Mitotic Phase (Mitosis and Cytokinesis)
What is a homologous chromosome?
chromosomes that are the same size, the same shape and the centromere is in the same place. They contain the same genes. One is maternal – from mum and one paternal- from dad.
How many chromosomes do the cells in the body contain?
46 chromosomes in 23 homologous pairs. Therefore when a new (daughter) cell is produced it will also contain 46 chromosomes.
What happens during interphase?
- DNA replicates,
- ATP synthesised,
- Organelles synthesised including centrioles,
- Proteins synthesised
How does DNA replication occur in Interphase?
Chromosomal DNA is replicated exactly and the two pieces of DNA are held together by the centromere.
Following mitosis the two new cells will contain one of each sister chromatids.
Why is mitosis important?
- ) need to produce genetically identical daughter cells
- ) Asexual reproduction - single celled organisms divide to produce daughter cells
- ) Growth - multicellular organisms grow by producing new extra cells
- ) Repair - damaged cells need to be replaced by new ones
- ) Replacement - red blood cells and skin cells need to be replaced.
What happens during Metaphase?
replicated chromosomes line up down the middle- equator of the cell. Each chromosome is attached to a different spindle fibre by its centromere
What happens during Anaphase?
the replicas of each chromosome are pulled apart from each other towards opposite poles of the cell. Identical sister chromatids are pulled to different poles by the shortening of the spindle fibres.
What happens during Prophase?
replicated chromosomes shorten and thicken (supercoil). Each chromosome consists of a pair of sister chromatids. Nuclear envelope breaks down and disappears. Centriole divides into two and each daughter centriole moves to opposite ends of the cell to form a spindle (protein threads).
What happens during Telophase?
two new nuclei are formed. Sister chromatids reach poles and are now chromosomes. Spindle breaks down and disappears chromosomes uncoil and can’t be seen in a light microscope any more.
When does Cytokinesis occur?
between telophase and interphase
How does cytokinesis occur in animal cells?
microtubules form a “draw string” just inside the membrane which then fuses as it is pinched in
How does cytokinesis occur in plant cells?
microtubules direct vesicles to the middle of the cell to form a cell plate, which forms a new cell wall. New cell surface membrane is made on either side to enclose the two cells
What is cancer?
mutation occurs (change in base sequences of DNA) in a gene that controls cell division, the cells can grow out of control (uncontrolled cell division), which can lead to the formation of tumours. Tumours can develop in any organ of the body, but are most commonly found in the lungs, prostate gland (male), breast and ovaries (female), large intestine, stomach, oesophagus and pancreas. A tumour becomes cancerous if it changes from benign to malignant.
How can cancer be treated?
often involves killing dividing cells by blocking part of the cell cycle. These treatments do not distinguish tumour cells from normal cells, however as tumour cells divide more frequently than normal cells the treatment is more likely to kill tumour cells. Normal body cells that rapidly divide such as hair producing cells are also vulnerable
Ways cancer drugs treat uncontrollable cell division?
- Preventing DNA from replicating. Radiation and some drugs damage DNA. If severe DNA damage is detected the cell will kill itself.
- Inhibiting the metaphase stage of mitosis by interfering with spindle formation.
- Preventing the synthesis of enzymes needed for DNA replication in S.
