A mutation is a change in the DNA sequence that can affect one or many nucleotides. There are two main types of mutations: point mutations, which change a single nucleotide, and chromosomal mutations, which change many nucleotides or an entire chromosome. Point mutations include substitutions, deletions, and insertions. Chromosomal mutations result from errors in mitosis or nondisjunction during meiosis, which leads to an imbalance of chromosomes.

1. WHAT IS A MUTATION?
a change in the sequence Can affect one or many
of DNA nucleotides
Mutation
Point mutation Error in mitosis
Chromosomal mutation

2. TYPES OF MUTATIONS
Point Mutation
Chromosomal Mutation
(Substitution)
 Change in only 1  Change in MANY
nucleotide nucleotides – up to a
 Ex. whole chromosome
AATCCGGCG  Ex.
AAACCGGCG

3. TYPES OF MUTATIONS – PART 2
1. Deletion = nucleotides are removed
 Ex. AATCCGGCG
AATCGGCG
2. Insertion = nucleotides are added
 Ex. AATCCGGCG
AATCCGGCCG
3. Inversion = order of nucleotides is reversed
 Ex. AATCCGGCG
GCGGCCTAA
 Usually occurs with big pieces of chromosomes

4. NONDISJUNCTION
 Definition = when pairs of chromosomes don’t
correctly separate during meiosis
 Results = an imbalance of chromosomes