Types of Mutations The power of the BASE!! . A MUTATION is a change in the DNA Chromosomal Mutations – affect MANY genes ex. Down syndrome 2) ***Gene mutations- affect a SINGLE gene – smaller effect . Frameshift Mutations Insertion – a new base is ADDED to a codon
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2) ***Gene mutations- affect a SINGLE gene – smaller effect
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.
ii. Point Mutation (base substitution) one base isEXCHANGEDfor 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
3. Nonsense- A STOPcodon before gene is done being translated (Stop codons are UAA, UAG, UGA)
Ex. UGG is Tryptophan but UGA is STOP
The disease causes muscle weakness. It usually leads to death by the mid 30s because muscles used to breathe also get weaker.
Duchenne’s Muscular dystrophy can be caused by a nonsense mutation. Look how much shorter the protein is.