Variation and mutation
- Created by: emews
- Created on: 01-12-17 11:49
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- Variation and mutation
- Individuals in a population are usually similar to each other, but not identical.
- Some of this variation within a species is genetic, some is environmental, and some is a combination of both.
- Children usually look a little like both their mother and their father because they get half of their inherited features from each parent.
- Each sperm cell and each egg cell contains half of the genetic information needed for an individual (each one is haploid)
- When these join at fertilisation, a new cell is formed.
- This zygote has all the genetic information needed for an individual (it is diploid)
- Each sperm cell and each egg cell contains half of the genetic information needed for an individual (each one is haploid)
- Examples of genetic variation in humans include blood group, skin colour and eye colour.
- Gender is also an inherited variation - whether you are male or female is a result of the genes you inherited from your parents.
- Mutation is a change in a gene or chromosome. It is a rare, random change in the genetic material and it can be inherited.
- Mutation can be spontaneous (it just happens). It can also happen because of:
- ionising radiation
- Ionising radiation includes gamma rays, X-rays and ultraviolet rays. The greater the dose of radiation a cell gets, the greater the chance of a mutation.
- chemical mutagens - such as tar from cigarette smoke
- ionising radiation
- A mutation may be neutral and have no effect.
- A mutation may sometimes be beneficial.
- Down’s syndrome is caused by the presence of three copies of chromosome 21 rather than just the usual two copies.
- It happens when a gamete (sperm cell or egg cell) forms abnormally during meiosis
- Mutation can be spontaneous (it just happens). It can also happen because of:
- Individuals in a population are usually similar to each other, but not identical.
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