Gene mutations
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GENE MUTATIONS. aka point mutations. Gene mutations which affect only one gene. DNA sequence ↓ mRNA sequence ↓ Polypeptide. Transcription. Translation. DNA (antisense strand) mRNA Polypeptide. Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons ↓ Pro-Glu-Glu-Cys-Gly

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GENE MUTATIONS

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Gene mutations

GENE MUTATIONS

aka point mutations


Gene mutations which affect only one gene

Gene mutations which affect only one gene

DNA sequence

mRNA sequence

Polypeptide

Transcription

Translation


Gene mutations

DNA (antisense strand)

mRNA

Polypeptide

Normal gene

GGTCTCCTCACGCCA

CCAGAGGAGUGCGGU

Codons

Pro-Glu-Glu-Cys-Gly

Amino acids

The antisense strand is the DNA strand which acts as the template for mRNA transcription


Mutations substitutions

Substitution mutation

GGTCACCTCACGCCA

CCAGUGGAGUGCGGU

Pro-Arg-Glu-Cys-Gly

Mutations: Substitutions

Normal gene

GGTCTCCTCACGCCA

CCAGAGGAGUGCGGU

Codons

Pro-Glu-Glu-Cys-Gly

Amino acids

Substitutions will only affect a single codon

Their effects may not be serious unless they affect an amino acid that is essential for the structure and function of the finished protein molecule (e.g. sickle cell anaemia)


The genetic code is degenerate

The genetic code is degenerate

A mutation to have no effect on the phenotype

Changes in the third base of a codon often have no effect.


No change

No change

Normal gene

GGTCTCCTCACGCCA

CCAGAGGAGUGCGGU

Codons

Pro-Glu-Glu-Cys-Gly

Amino acids

Substitution mutation

GGTCTTCTCACGCCA

CCAGAAGAGUGCGGU

Pro-Glu-Glu-Cys-Gly


Disaster

Disaster

Normal gene

GGTCTCCTCACGCCA

CCAGAGGAGUGCGGU

Codons

Pro-Glu-Glu-Cys-Gly

Amino acids

Substitution mutation

GGTCTCCTCACTCCA

CCAGAAGAGUGAGGU

Pro-Glu-Glu-STOP


Mutations inversion

Mutations: Inversion

Inversion mutations, also, only affect a small part of the gene

Inversion mutation

GGTCCTCTCACGCCA

CCAGGAGAGUGCGGU

Pro-Gly-Glu-Cys-Gly

Normal gene

GGTCTCCTCACGCCA

CCAGAGGAGUGCGGU

Codons

Pro-Glu-Glu-Cys-Gly

Amino acids


Mutations additions

Mutations: Additions

A frame shift mutation

Normal gene

GGTCTCCTCACGCCA

CCAGAGGAGUGCGGU

Codons

Pro-Glu-Glu-Cys-Gly

Amino acids

Addition mutation

GGTGCTCCTCACGCCA

CCACGAGGAGUGCGGU

Pro-Arg-Gly-Val-Arg


Mutations deletions

Mutations: Deletions

A frame shift mutation

Deletion mutation

GGTC/CCTCACGCCA

CCAGGGAGUGCGGU

Pro-Gly-Ser-Ala-Val

Normal gene

GGTCTCCTCACGCCA

CCAGAGGAGUGCGGU

Codons

Pro-Glu-Glu-Cys-Gly

Amino acids


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