Biology - Cell division and stem cells Flashcards
What are chromosomes?
Chromosomes carry genetic information in a molecule called DNA. They are found in pairs in the nucleus of the cell, and consist of a linear arrangement of genes. Each human body cell contains 46 chromosomes. These can be arranged into 23 pairs. Each chromosome in a pair carries the same types of genes.
What is the process of mitosis?
A type of cell division which produces daughter cells identical to the parent.
-Mother cell has 4 chromosomes
-DNA replicates to make two of each chromosome
-Nuclear membrane breaks, chromosomes form line down middle
-one set of chromosomes pulled to each side whilst nucleus divides
-two identical daughter cells produced.
What is the function of mitosis?
Occurs for growth, to replace worn out cells, and to repair damaged cells
What is cancer caused by?
Cancer is the result of uncontrolled mitosis. The uncontrolled growth causes a lump called a tumor to form.
What are lifestyle factors that could cause cancer?
-The chemical carcinogens in cigarette smoke increasing the risk of lung cancer.
-Alcohol intake is linked with certain cancers.
-Exposure to ultraviolet radiation, part of which is ionising, during sunbathing or outdoor activities, leading to the development of skin cancers.
-A poor diet with increased fat and salt intake, as well as the consumption of certain foods, can increase the risk of cancer.
What are Industrial and environmental factors that could cause cancer?
-Exposure to ionising radiation, like ultraviolet radiation in sunlight, increases the risk factor.
-Exposure to chemical carcinogens such as those in cigarette smoke.
What is the function of meiosis?
Formation of sex cells(gametes) like eggs and sperm for sexual reproduction.
What is the process of meiosis?
- Mother cell has 4 chromosomes. (4 chromosomes, 2 pairs)
- DNA replicates but the chromosome and its copy remain attached. (8 chromosome, 4 pairs)
- One of each pair of chromosomes goes into a new cell. (4 chromosomes, 2 pairs)
- One chromosome from each pair goes into a new cell. ( 2 chromosomes)
- 4 new cells are formed.
- Each cell has half the chromosomes the mother cell has - they are haploid.
- Cells are not genetically identical to the mother cell.
What is the difference between meiosis and mitosis?
Mitosis - Produces genetically identical daughter cells
Meiosis - Produces genetically varied daughter cells
Mitosis - Daughter cells have a full set of chromosomes
Meiosis - Daughter cells have half a set of chromosomes
Mitosis - Two daughter cells are produced
Meiosis - Four daughter cells are produced
Mitosis - Occurs for growth, to replace worn out cells, and to repair damaged cells
Meiosis - Occurs for the formation of gametes in sexual reproduction
What are stem cells?
An embryo develops from a fertilised egg. Cells in the early stages of the development of an embryo are known as stem cells. Stem cells are undifferentiated cells that can differentiate into any other type of cell.
Where can adult stem cells be found?
brain
eyes
blood
heart
liver
bone marrow
skin
muscle
What is the difference between adult stem cells and embryonic stem cells?
Embryonic - If cells are removed from the embryo they will differentiate into any cell type. These are called embryonic stem cells.
Adult - Adult stem cells can differentiate into related cell types only, for instance, bone marrow cells can differentiate into blood cells and cells of the immune system, but not other cell types.
How can human stem cells be used?
Stem cells can divide to produce new cells, which can then divide into different cell types. They therefore have the potential to be transplanted into patients to treat medical conditions and disease. They could be used to replace cells that have been damaged or destroyed, for example:
in type 1 diabetes
in cases of multiple sclerosis, which can lead to paralysis
in cases of spinal cord or brain injury, which have led to paralysis
What are the benefits associated with the use of stem cells in medicine?
Stem cells have great potential, eg in treating patients with currently untreatable conditions, growing organs for transplants, and research.
no rejection
no need to find a donor
What are the ethical issues of using stem cells in medicine?
-One source of embryonic stem cells is unused embryos produced by in vitro fertilisation (IVF).
-Embryos could come to be viewed as a commodity, and not as an embryo that could develop into a person.
-At what stage of its development should an embryo be regarded as, and treated as, a person?
