Mutations Lecture Honors Biology Ms Day Review Mutations

Mutations Lecture Honors Biology Ms. Day

Review…

Mutations n Mutation n. A change (mistake) in the DNA of a cell 2 MAIN TYPES n 1. Point mutations n 2. Frameshift mutations

POINT MUTATIONS n Definition: Change in a single nucleotide in DNA strand n Aka: Base-pair substitutions

Point Mutations n. Can results in a mutation (change) that is n harmful n neutral §not harmful or helpful n beneficial

3 TYPES OF POINT MUTATIONS 1. Missense n 1 wrong amino acid is added to polypeptide (Ex: Sickle Cell Anemia) 2. Nonsense n n A change in DNA leads to EARLY STOP codon!!! Polypeptide is SHORTEN!! § Ex: ATA on DNA UAU (Try) ATT UAA (stop not Try)

POINT MUTATION ANALOGY… n TEMPLATE: THE CAT ATE THE RAT n POINT MUTATION: THE CAT ATE THE RAT n THE CAT ATE THE BAT What kind of point mutation is this? n MISSENSE n THE CAT ATE THE XAT What kind of point mutation is this? n NONSENSE

3 TYPES OF POINT MUTATIONS 3. Silent n DNA is mutated leads to different codon BUT same amino acid § Ex: ATA on DNA UAU (Try) ATG UAC (STILL Try) Why does this happen? What is the effect on the protein?

Frameshift Mutations n. Insertions & deletions n. Add or subtract 1 nucleotide n 2 TYPES § Insertion § Deletion

FRAMESHIFT MUTATION ANALOGY… n TEMPLATE: THE CAT ATE THE RAT n ADDITION of “B” MUTATION: THE CAT ATE THE RAT THE CAT BAT ETH ERA T What kind of frameshift mutation is this? n INSERTION n SUBTRACTION of “A” MUTATION: THE CAT ATE THE RAT n THE CAT TET HER AT What kind of frameshift mutation is this? n DELETION n

Which is more harmful? n Typically, frameshift mutations are more harmful BUT some point mutations can be LETHAL n Ex: Tay Sachs and Cystic Fibrosis

Causes of Mutations n Inherited mutations n From mom and dad n Spontaneous mutations n occurs during DNA replication n DNA Polymerase MISS mistakes not proofreading! n Environmental mutations (Mutagens) n Physical/chemical n Ex: Sun, viruses, chemicals