1. Mutations

2. Protein synthesis summary
DNA A C T G C G A U
mRNA
transcription
nucleus
Gly
Ser
Phe
Trp
PROTEIN
translation
Cytoplasm:
ribosome

3. Definition: A mutation is…
A change in the arrangement of bases in an individual gene or in the structure of the chromosome (which changes the arrangement of genes).

4. Frequency and repair of mutations
Mutations can occur in gametes and somatic cells.
Chance of mutation is between 2-30 x 10-7
Faulty DNA can be repaired by specific enzymes.
Unrepaired mutations will affect the new proteins being synthesised

5. Point mutations are caused by:
Changes in an individual gene due to miscopying of one or more nucleotides.
Deletion or insertion of a nucleotide results in a frameshift:
C A T G C G A
T C A G A T
Codon 1
Codon 2
Codon 3
Codon 4
Val
Tyr
Arg
Ala
Ser
Leu

6. Point mutations T A C G T G A A A T C G G C A T Met His Phe Leu Ala
Substitution mutations result in a change of one base:
T A C G T G A A A T
C G G C A T
Met
His
Phe
Leu
Ala
Val

7. Chromosomal mutations
Gene deletion: A B C D E
Gene duplication: C D B A E E C D B A

8. Chromosome mutations B A C D E B A C D E W X Z Y Inversion:
Translocation: B A C D E W X Z Y

9. Whole-chromosome mutations
An entire chromosome is lost or repeated during cell division.
Example: Downs syndrome is caused by having an extra chromosme 21.

10. The effect of mutations
Production of new/superior protein: Results: gain of reproductive advantage
Neutral mutation: Result: No change
Production of inferior or no protein: Result: Fatal and/or disease causing.

11. Causes of mutations
Mutagens such as: X-rays ionising radiation chemicals

12. Summary Define the term: translocation somatic duplication deletion
mutation
insertion
inversion
Down’s syndrome
mutagen