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41 Cards in this Set
- Front
- Back
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Which cells undergo cell division? |
Eukaryotic cells |
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What are the 2 stages of cell division? |
The interphase The mitotic phase |
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What are the stages in the interphase? |
Growth phase 1 Synthesis Growth phase 2 |
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What happens in growth stage 1? |
The cell grows The number of organelles increases Proteins are made ATP is synthesised |
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What happens in synthesis? |
Semi-conservative DNA replication |
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What happens in growth stage 2? |
The cell continues to grow
Proteins are made ATP is synthesised |
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What are the stages of the mitotic phase? |
Mitosis Cytokinesis |
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What happens in mitosis? |
Nuclear division |
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What happens in cytokinesis ? |
The cytoplasm divides |
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Which human cells contain chromosomes and how many are there? |
Somatic cells (non-sex cells) 46 chromosomes |
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What do the 46 chromosomes form? |
23 homologous pairs which are the same size, shape and have a centromere in the same place. |
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What happens in the interphase? |
DNA replicates ATP is synthesised Organelles are synthesised Proteins are synthesised |
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What happens to DNA replication in the interphase? |
Chromosomal DNA is replicated exactly and 2 pieces of DNA are held together by the cntromere. 1 chromosome turns into 2 geneticaly identical chromatids. |
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What happens if the copies are not done accurately? |
Mutations may occur and the daughter cells won't receive identical genetic material. |
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What is mitosis important for? |
Organisms which need to produce genetically identical daughter cells. Asexual reproduction Growth Repair Replacement |
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What happens when repair takes place? |
Damaged cells are replaced by new ones which perform the same function to repair the tissue |
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What are the stages of mitosis? |
Prophase
Metaphase Anaphase Telophase |
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What happens in the prophase? |
Replicated chromosomes supercoil(shorten and thicken). The nuclear envelope breaks down and disappears. The centriole divides into 2 and each centriole moves to opposite poles of the cell to form a spindle. The nucleolus disappears. |
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What is the spindle ? |
Protein threads |
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What happens in the metaphase? |
The replicated chromosomes line up in the middle of the cell. Each chromosome is attached to a different spindle fibre by the centromere. |
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What happens in the anaphase? |
The replicas of the 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 and the centromere splits. |
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What happens in the telophase? |
Two new nuclei are formed. The sister chromatids reach the poles and are ow chromosomes. The spindle breaks down and disappears whilst the nucleolus reappears. Chromosomes uncoils and can no longer be seen by a light microscope. |
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What happens during cytokinesis in an animal cell? |
Microtubules form a draw string just inside the membrane which then fuses as it's pinched in. |
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When does cytokinesis occur? |
Between the telophase and interphase |
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What happens during cytokinesis in a plant cell? |
Microtubules direct vesicles to the middle of the cell to form a cell plate which forms a cell wall. New cell surface membrane is made on either side to enclose the 2 cells |
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Which plant cells can divide? |
Only meristem cells e.g. root tip/ shoot tip/ cambium |
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What happens to mass of cell and DNA in the cell cycle? |
It increases as genetic material replicates and then decreases when 2 seperate cells are formed. |
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What controls the cell cycle? |
Genes |
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What causes cancer? |
A mutation in the gene that controls cell division can cause cells to grow out of control. This can lead to the formation of tumours. |
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When does a tumour become cancerous? |
When it changes for benign to malignant |
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What is the difference between a benign and a malignant tumour? |
Benign tumours don't affect the cells around them, whereas malignant tumours do |
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What does cancer treatment usually involve? |
Killing dividing cells by blocking part of the cell cycle. The cell cycle is disrupted and so cell division/ cancer growth stops. |
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What is a problem with cancer treatments? |
They can't distinguish tumour cells from normal cells however it's more likely to kill tumour cells as they divide more frequently. This means, normal cells which divide rapidly (hair cells) are vulnerable. |
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How do drugs treat cancer? |
They prevent DNA from replicating. Radiation and some drugs damage DNA and if severe damage is detected, the cell will kill itself. They inhibit metaphase by interfering with spindle formation. They prevent synthesis of enzymes needed for DNA replication in G1. |
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When do human cells have 24 chromosomes? |
Anaphase and telophase as the chromatids separate. |
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What happens to the mass of DNA in the 3 main stages of cell division? |
It doubles in mitosis, is 1x in cytokinesis and doubles halfway through interphase |
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How many chromosomes are in a human red blood cell? |
None, as there's no nucleus |
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Why can only meristems divide? |
Plant cell walls stop the from being able to divide effectively. Meristems have very thin cell walls |
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Why doesn't mitosis take place in bacterial cells? |
It has no linear DNA, no nucleus and therefore no chromosomes. |
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What are homologous pairs? |
Pairs of matching chromosomes, one is from the mother and one is from the father. We have 23 pairs. |
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What is asexual reproduction? |
The production of genetically identical offspring from one parent. There's no genetic variation. For example, sea anemones. |
