Mutation and Mutagens

mutation

Alteration in the nucleic acid sequence of the organism

mutation

Permanent change of the nucleotide sequence

mutation

When the structure changes, function changes.

fitness or survival

Mutation Beneficial: advantages to bacteria, leading to increased — in their environment.

reduced viability or disease

Mutation Harmful: decrease the organism’s fitness potentially leading to —

Spontaneous

occurs due to natural causes

Spontaneous

arises naturally

Spontaneous

without external factors

Point, Frameshift, Rearrangement, Gene duplication, Inversion, Translocation

spontaneous effects on dna structure

induced

Occurs due to mutagens from the environment

induced

Arises due to outside factors

Missense, Nonsense, Silent, Conservative, Non-Conservative

induced effects on resulting protein

point mutation

Involves changing the single base in the DNA sequence

point mutation

This mistake is copied during replication to produce a permanent change.

replication

point mutation: This mistake is copied during — to produce a permanent change.

point mutation

substitution only

Missense , Nonsense , Silent

point mutation can result to

silent point mutation

Mutated codon codes for the same amino acid

missense point mutation

Mutated codons code for a different amino acid

nonsense point mutation

mutated codon is a premature stop

Conservative Missense Mutation

Amino acid is similar in function and shape to the amino acid being replaced

Conservative Missense Mutation

Results in a protein with almost identical functionality and shape as that of the original protein.

Non-Conservative Missense Mutation

Amino acid is completely different in function and shape to the amino acid being replaced

Non-Conservative Missense Mutation

Results in a protein with completely different functionality and shape as that of the original protein.

frameshift mutation

Involves changing one or more nucleotide base in the DNA sequence

frameshift mutation

Changes the code for all amino acids

insertion , deletion

frameshift mutation can be classified into:

reversion

Restores the original function of a gene by directly reversing the effects of a previous mutation.

reversion

Occurs at the same site as the original mutation (true reversion) or near it, restoring the original phenotype.

reversion

A point mutation changing a codon from UAU (tyrosine) to UAA (stop codon) is reversed back to UAU, restoring tyrosine production.

suppression

A secondary mutation that compensates for the effects of a primary mutation, restoring functionality without reversing the original mutation.

suppression

Often occurs at a different site in the genome (intragenic or extragenic suppression).

suppression

A tRNA mutation that allows it to recognize and insert the correct amino acid at a stop codon caused by the original mutation.

physical mutagens

Non-ionizing radiation – UV light that causes the formation of thymine dimers and visible light.

physical mutagens

Non-ionizing radiation – UV light that causes the formation of thymine dimers and visible light.

physical mutagens

Heat- can denature DNA

intercalating agent , alkylating agents , base analogs, metal ions

chemical mutagens

intercalating agent

molecules resembling the ring structure of bases

alkylating agents

adds alkyl groups to DNA bases

base analogs

resemble DNA bases

metal ions

cause DNA hypermethylation