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Genetic changes
Mutation—a change in the DNA sequence of an organism.
Mutations are not always harmful. Any change to DNA that leads to a
different trait is a mutation. It could be a beneficial change, too.
Mutations can occur in the DNA of either gametes (egg/sperm) or
body cells.
WHICH TYPE WOULD HAVE MORE LASTING EFFECTS?
Mutations in gametes will be passed to the offspring.
Types of mutations
1. Point mutations—a change in a single base of a DNA chain.
This results in a different “message.”
Example: normal sequence  THE DOG BIT THE CAT
mutation  THE DOG BIT THE CAR
Sense mutation: the changed codon makes a different
amino acid.
Nonsense mutation: the change makes a “stop” codon (no
amino acid is made).
2. Frameshift mutations—a base is deleted or added to a
sequence. Every codon after the mutation is changed.
Example: normal sequence  THE DOG BIT THE CAT
If the “G” was deleted THE DOB ITT HEC AT
WHICH TYPE OF MUTATION IS MORE SIGNIFICANT?
Other possible mutations
Chromosomal mutation—occurs when chromosomes are
dividing, they may break and not join back together correctly.
Non-disjunction—this occurs when chromosomes do not
separate during meiosis. This results in a gamete with two
chromosomes and one with no chromosomes.