mutations. a c cc t a a aa g g t dna c c g g g a a u u uuu mrna transcription nucleus gly ser phe...

Mutations

Protein synthesis summary

A C C CTA A A AG G TDNA

C CG G GA AUU U U UmRNA

transcriptionnucleus

GlySerPheTrp PROTEIN

translationCytoplasm: ribosome

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).

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

Val

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 T C A G A TA

Codon 1 Codon 2 Codon 3 Codon 4

Tyr Ala Ser LeuArg

Point mutations

Substitution mutations result in a change of one base:

T A C G T G A A A C G G C A T

Met His Phe Ala Val

T

Leu

Chromosomal mutations

Gene deletion:

A B C D E

Gene duplication:

EC DBA C DC DBA E

Chromosome mutations

Inversion:

C DBA E

Translocation:

BA C D E

WX ZY

Whole-chromosome mutations

An entire chromosome is lost or repeated during cell division.

Example:Downs syndrome is caused by having an extra chromosme 21.

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.

Causes of mutations

Mutagens such as:

X-rays

ionising radiation

chemicals

Summary

Define the term:

somatic

mutation

deletion

insertion

duplication

inversion

translocation

Down’s syndrome

mutagen

www.clickbiology.com