Powerpint mutation
- 1. SOURCE OF VARIATION: MUTATIONIs a change in a gene orchromosome
- 2. 14MutationsA mutation is a spontaneous change in a gene or chromosomeGene mutations may arise when a gene fails to make an exactcopy of itself during replication prior to meiosis or mitosisChromosome mutations can result from:-Damage to, or loss of a chromosome-Incomplete separation of chromosomes at meiosis leading to extra chromosomes in one gamete-Part of a chromosome becoming attached to another chromosome (translocation)- Doubling the whole set of chromosomes
- 3. 22Chromosome mutations in humans usually result in spontaneous abortion of the foetusBut a proportion survive e.g.Downs syndrome: The affected person has one extra chromosome in their genome (i.e. 47 instead of 46 chromosomes) This results in characteristic facial features, varying degrees of mental impairment and, usually, a very cheerful dispositionKlinefelters syndrome. The affected male has an extra X chromosome (XXY)The person appears to be a normal male but he is infertileChromosome mutations in humans
- 4. 25-A mutated gene which is dominant, or inherited as a homozygousrecessive, will affect the whole organism-A mutated gene which does not result in abortion or early deathof an organism will be inherited by the offspring -Very rarely, a mutation will be beneficial and will be inherited bythe offspringGene mutations in humans may result in:AlbinismSickle cell anaemiaHaemophiliaCystic fibrosisDwarfismColour blindnessMutations
- 5. 26-If a gene mutation takes place in a gamete which contributes toa zygote, the mutation will affect the whole organism-A gene mutation in a body cell will affect only that cell and any cells derived from it.It is mutations in body cells which give rise to cancers.-These mutations usually affect the genes which control cell division-The control on cell division is reduced so that the cell dividesrepeatedly, giving rise to a tumour
- 6. 30MutagensSome environmental effects may increase the mutation rate.These include radiation (X-rays, ultra-violet, radioactive materials) and carcinogenic chemicals such as those in tobacco smokeThese are all known as mutagens-Mutagens which affect body cells may produce cancers. -Mutagens affecting the reproductive organs may result in defective offspring
- 7. Question 135Chromosome mutations can occur as a result of…(a) gain of an extra chromosome(b) doubling of the entire set of chromosomes(c) faulty replication of DNA(d) breaking of a chromosome
- 8. 36Question 2Gene mutations can occur during DNA replicationprior to …mitosis(b) meiosis
- 9. Question 337Sickle cell anaemia results from …a change in a nucleotide triplet(b) a change in a single nucleotide(c) a change in a single amino acid(d) a chromosome mutation