Mutations in DNA

1. Mutations in DNA • changes in the DNA sequence that can be inherited • can have negative effects (a faulty gene for a trans-membrane protein leads to cystic fibrosis), but most mutations go unnoticed (we have two copies of each gene). melanoma

2. Point Mutations Silent Mutations • have no effect on cell function (two types) • Errors that are located in intron regions - get cut out before translation. • Genetic code redundancy - a change in the sequence may not alter the amino acid (eg. UUU and UUC both result in phenylalanine)

3. Point Mutations (cont.) Missense Mutation • When a change in the sequence of DNA alters a codon, resulting in a different amino acid being put in the peptide sequence. • Sickle cell anemia occurs because of a missense mutation.

4. Point Mutations (cont.) Nonsense Mutation • A change in the DNA sequence causes a STOP codon to be inserted in place of an amino acid codon. • The protein produced is truncated (too short). • Found in Duchenne Muscular Dystrophy

5. Point Mutations (cont.) Frameshift Mutations causes the reading frame for codons to change. • Can result from deletions of nucleotides from the DNA sequence or from insertions of nucleotides into the sequence. • Either way, it shifts the reading frame in translation and results in a completely different sequence of amino acids being constructed. • Note that inserting or deleting 3 bases in the DNA wouldn’t shift the reading frame, it just adds or removes an amino acid.

6. Frameshift Mutations

7. Major Mutations