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Mutations
Chapter 12
What is a mutation?
• Mutations are changes in the DNA or
RNA sequence that affect genetic
information.
• At the molecular level, mutations are
usually caused by errors made during
DNA Replication, Protein Synthesis, etc.
However, sometimes environmental
factors can cause mutations. It simply
depends on the type of mutation.
Types of Mutations
• Gene Mutations result from changes
in a single nucleotide. They are at the
DNA / RNA level.
▫ Point Mutations
▫ Frameshift Mutations
• Chromosomal Mutations involve
changes in parts of chromosomes.
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Deletion
Duplication
Inversion
Translocation
Gene Mutations
• Point Mutations are mutations that are only
affected at one nucleotide.
• Example:
▫ ORIGINAL STRAND:
 ATTGCC
▫ MUTATED COMPLEMENT STRAND:
 TAACGC
Gene Mutations
• Frameshift Mutations involve
the insertion or deletion of a
nucleotide. This causes a change in
the entire reading frame.
• Example:
▫ ORIGNAL DNA STRAND:
 ATTGCC
▫ MUTATED mRNA COMPLEMENT
STRAND:
 UAAGG
Think of gene mutations, and its
effects on a normal sentence.
• Original Sentence:
▫ TIME TO DREAM
• Point Mutation:
▫ TAME TO DREAM
• Frameshift Mutation / Deletion:
▫ TETO DR EAM__
• Frameshift Mutation / Insertion:
▫ TIIM ET ODREAM
Chromosomal Mutations
• Deletion occurs when one or more genes is lost
in a chromosome.
Chromosomal Mutations (cont)
• If a gene is inserted more than once on a
chromosome, it is called duplication.
Chromosomal Mutations (cont)
• During inversion, part of a chromosome gets
reversed from its original direction.
Chromosomal Mutations (cont)
• Translocation describes when one part of a
chromosome breaks off and attaches to a
homologous chromosome.
▫ This is called crossing-over and occurs naturally
during Meiosis!
Chromosomal Mutations (cont)
The good, the bad, and the ugly
• Most mutations are disadvantageous
(harmful), but some mutations are
advantageous (good). These good
mutations allow species to adapt as
environmental factors fluctuate.
• In other cases, mutations
simply make a change that
is neither good not bad.
Why are mutations important?
• Mutations facilitate biodiversity
as well as evolution.
▫ Biodiversity = variety of
species on earth
▫ Evolution = change over time
• If species do not adapt to
changes in the environment,
they will become extinct.