Types of Mutations
The power of the BASE!!
A MUTATION is a change in the DNA
1) Chromosomal Mutations – affect MANY genes ex.
Down syndrome
2) ***Gene mutations- affect a SINGLE gene – smaller
effect
i.Frameshift Mutations
1.Insertion – a new base is ADDED to a codon
INSERT A “G” 
ex. AUG UAC GGU
AUG GUAC GGU
AUG GUA CGG U
2. Deletion – a base is REMOVED from a codon
REMOVE THE “U” 
ex. AUG
UAC GGU
AUG
AC GGU
AUG
ACG
GU
• Huntington Disease: Caused by an Insertion
Mutation. You die young (40s or 50s) but you
don’t normally know you have it until after
you have passed it on to your children.
• Cystic Fibrosis is a disease sometimes caused by
a deletion of a single T base. The hallmark
symptoms of cystic fibrosis are salty tasting
accumulation of thick, sticky mucous, frequent
lung infections, coughing, shortness of breath.
• Inherited (Recessive Trait)
ii. Point Mutation (base substitution) one base is
EXCHANGED for another
1. Missense- a NEW amino acid is coded for
Ex. UUU is Phenylalanine
Ex. UUA is Leucine
• Sickle cell anemia is caused by a single base
substitution!!! The “sickle” shaped red blood
cells don’t carry oxygen as well.
2. Silent – no CHANGE in the amino acid
sequence
Ex. CCC is Proline
Ex. CCG is Proline
Examples of disease caused by SILENT mutations….????
3. Nonsense- A STOP codon before gene is
done being translated (Stop codons are UAA,
UAG, UGA)
Ex. UGG is Tryptophan but UGA is STOP
!
Duchenne’s Muscular dystrophy
can be caused by a
nonsense mutation. Look
how much shorter the
protein is.
The disease causes muscle
weakness. It usually
leads to death by the
mid 30s because muscles
used to breathe also get
weaker.