Mutations
- Created by: jaymelouise2
- Created on: 17-04-15 15:01
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- Mutations
- Chromosome Mutations
- involves random changes to the structure of a chromosome.
- Inversion: a section of chromosome turns through 180 degrees.
- Deletion: a part is lost.
- Translocation: a piece of one chromosome becomes attached to another.
- Non-disjunction: homologous chromosomes fail to separate properly at meiosis 1 or chromatids fail to separate at meiosis 2.
- DNA Mutations
- Changes to genes due to changes in nucleotide base sequences
- Could happen when DNA is replicating before nuclear division by either mitosis or meiosis.
- Mitosis: somatic mutations that aren't passed on to the offspring. Can add to the ageing process or may lead to cancer.
- Meiosis: mutations can be inherited.
- 2 Main Classes
- Point/substitution mutations
- One base pair replaces another.
- Insertion/deletion mutations
- One or more nucleotide pairs are inserted or deleted from a length of DNA.
- Point/substitution mutations
- The effects on the polypeptide sequence..
- Missense mutation: causes one AA to swap for another.
- Nonsense mutation: causes a stop codon to be produced. Protein too short so can't function now.
- Silent mutation: happens in a non-coding part of DNA or causes the same AA to be put in place.
- Frameshift: every AA after that point is changed.
- Diseases
- CF: deletion of a triplet of base pairs. Effects whole function of Cl¬ pump
- Sickle-cell An: point=missense on codon 6. Valine instead of glutamic acid.
- Bladder cancer: point in RAS gene, produces oncogenes = unreg cell div.
- Huntingtons: repeating CAG sequence (insertion) alters protein
- Effects
- Neutral
- If mutation is in non-coding part or if its a silent mutation
- If the changed charac gives no particular ad or disad to organism
- Eg some people can smell honeysuckle flowers and some can't
- Harmful/beneficial
- Skin colour
- Africa, lots of UV light so handy to have dark skin as pigment melanin protects them from UV effects. Could still make vit D
- More temperate climes.. less intense so dark skin couldn't make vit D.
- Mutations producing paler skin is an ad as they could make more vit D
- So diff environ alters whether the mutation is good or bad
- Skin colour
- Neutral
- a random change to genetic material in a cell, could be the amount of or arrangement of it.
- May occur during DNA replication. May be caused by substances called mutagens.
- Tar
- UV light
- X-rays and gamma rays.
- Chromosome Mutations
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