Cell Division (Edexcel GCSE Combined Science: Biology): Flashcards
Exam code: 1SC0
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Mitosis
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Mitosis
A nuclear division that gives rise to two genetically identical diploid daughter cells.
Diploid cell
A cell containing the full number of chromosomes (in humans, 23 pairs).
Which type of cells are produced by mitosis?
All body cells (not gametes).
State three processes that require mitosis.
Growth — produces new cells
Repair — replaces damaged or dead cells
Asexual reproduction — produces genetically identical offspring
What are the three parts of the cell cycle?
Interphase
Mitosis
Cytokinesis
What happens during interphase?
The DNA in the nucleus copies itself exactly, forming X-shaped chromosomes.
What happens during cytokinesis?
The cell cytoplasm and membrane divide to produce two daughter cells, each with a copy of every chromosome.
List the four stages of mitosis in order.
Prophase
Metaphase
Anaphase
Telophase
What happens during prophase and metaphase?
Prophase: DNA condenses, chromosomes become visible and the nuclear membrane breaks down
Metaphase: chromosomes line up on the equator of the cell
What happens during anaphase?
Spindle fibres split the chromosomes and pull one chromatid to either side of the cell.
During telophase, new form around the chromosomes at either end of the cell.
During telophase, new membranes form around the chromosomes at either end of the cell.
If one cell divides 7 times, the number of cells produced is 2 to the power 7, which equals cells.
If one cell divides 7 times, the number of cells produced is 2 to the power 7, which equals 128 cells.
True or False?
DNA is copied during prophase, the first stage of mitosis.
False.
DNA is copied during interphase, before mitosis begins. In prophase the DNA condenses and the chromosomes become visible.
Tumour
A mass of cells formed as a result of uncontrolled cell growth and division.
Cancer
A disease caused by mutations in the DNA of cells that lead to uncontrolled cell growth and division.
Why do body cells normally divide by mitosis?
For growth and to repair damaged cells.
What ensures cells divide only when needed and stop when required?
The cell cycle is regulated by many different genes.
What causes cancer?
Mutations in the DNA of cells that lead to uncontrolled cell growth and division, which can form a tumour.
What are the two main types of tumour?
Benign tumours
Malignant tumours
Describe a benign tumour.
A growth of abnormal cells contained in one area, usually within a membrane. It does not invade other parts of the body and is not cancerous.
Describe a malignant tumour.
A cancerous tumour whose cells invade neighbouring tissues and spread to other parts of the body via the blood and lymphatic system, forming secondary tumours.
Why are malignant tumours dangerous?
They invade and disrupt the functioning of the organ they originate in and the organs they spread to, which can lead to death.
tumours do not invade other parts of the body, whereas tumours are cancerous and spread.
Benign tumours do not invade other parts of the body, whereas malignant tumours are cancerous and spread.
Malignant tumour cells spread around the body via the blood and system.
Malignant tumour cells spread around the body via the blood and lymphatic system.
True or False?
Cancer is caused by mutations in the genes that control the cell cycle.
True.
Mutations stop the cell cycle being regulated properly, so cells divide uncontrollably and can form a tumour.
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