types of mutations

Types of Mutations

Thanks to Ms. Sara Dozier and Ms. Kimball for many of these slides!

Mutations•Mistakes in the nucleotide sequence in the DNA of a cell

•Caused by:

•Errors during DNA replication

•UV light

•Radiation

•Toxic chemicals

•Some viruses

•Immune system

What is a Mutant?

We are ALL Mutants!

Why Mutate?• Mutations are a natural source of variation

• Variety in a population is good!

• Variation is essential to evolution

• SOME mutations are good: help an organism survive and reproduce

• SOME mutations are bad: cause disease or death

•MOST mutations are neutral: do not help nor hurt

•Often repaired or not expressed

Do Mutations Matter?• Antibiotic resistance is due to mutations (GOOD for bacteria, BAD for us)• Tay Sachs Disease is due to a frame shift mutation (BAD for humans)• Some people are resistant to HIV infection due to a mutation in an immune cell receptor CCR5 (GOOD for those lucky ones!)

HIVHIV is a virus - it’s not considered a living thing because it needs a host cell to reproduce and make proteins

HIV affects the immune system, making it hard for an infected person to fight off other diseases

HIV has a high mutation rate, which means it’s constantly changing and evolving

This makes it very difficult to create a cure or vaccine

Point Mutation•A single base in the DNA sequence is changed to another base

•3 types of point mutations:

•Silent

•Missense

•Nonsense

Silent Mutation•Type of point mutation

•A nucleotide base changes, but the amino acid stays the sameORIGINAL DNA: TAC CGT ACG GAT AAG ACT

ORIGINAL AA: MET ALA CYS LEU PHE STOP

MUTATED AA: MET ALA CYS LEU PHE STOP

ORIGINAL RNA: AUG GCA UGC CUA UUC UGAMUTATED RNA: AUG GCA UGU CUA UUC UGA

MUTATED DNA: TAC CGT ACA GAT AAG ACT

Missense Mutation

•Type of point mutation

•A nucleotide base changes which results in an amino acid to changeORIGINAL DNA: TAC CGT ACG GAT AAG ACT

MUTATED DNA: TAC TGT ACA GAT AAG ACT

ORIGINAL AA: MET ALA CYS LEU PHE STOP

MUTATED AA: MET THR CYS LEU PHE STOP

ORIGINAL RNA: AUG GCA UGC CUA UUC UGAMUTATED RNA: AUG ACA UGC CUA UUC UGA

Nonsense Mutation

•Type of point mutation

•A nucleotide base changes which causes an early stop codonORIGINAL DNA: TAC CGT ACG GAT AAG ACT

MUTATED DNA: TAC CGT ACT GAT AAG ACT

ORIGINAL AA: MET ALA CYS LEU PHE STOP

MUTATED AA: MET ALA Stop

ORIGINAL RNA: AUG GCA UGC CUA UUC UGAMUTATED RNA: AUG GCA UGA CUA UUC UGA

Other types of Mutations

•Reading Frames

•Frameshift mutations

•Insertion of an extra nucleotide OR

•Deleting of a nucleotide