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Mutations
Mutations are changes
in genetic material
 Mutations that produce
a change in a single
gene are gene mutations
 Mutations that change a
whole chromosome are
chromosomal mutations
Gene mutations that involve
only a few nucleotides are
point mutations.
3 Types of point mutations
Substitutions – one base is
changed to another
Insertions – a base is added
Deletions – a base is left out
Insertion or deletion
mutations are also known as
frameshift mutations because
the codons are still read in
3’s and this “shifts” all the
codons following the change.
Examples:
Substitution mutation
DNA: TAC GCA TGG AAT
mRNA: AUG CGU ACC UUA
Amino
acids: Met Arg Thr Leu
Substitution of T for a C
DNA: TAC GTA TGG AAT
mRNA: AUG CAU ACC UUA
Amino acids: Met His Thr Leu
Insertion Mutation
DNA: TAC GCA TGG AAT
mRNA: AUG CGU ACC UUA
Amino
Acid: Met Arg Thr Leu
Insert a T
DNA: TAT CGC ATG GAA T
mRNA: AUA GCG UAC CUU A
Amino
Acid: Ile Ala Tyr Leu
Deletion mutation
DNA: TAC GCA TGG AAT
mRNA: AUG CGU ACC UUA
Amino
acids: Met Arg Thr Leu
Delete A
DNA: TCG CAT GGA AT
mRNA: AGC GUA CCU UA
Amino
acid : Ser Val Pro
Chromosomal mutations involve
changes in the number or
structure of chromosomes. It is
possible to delete, duplicate,
invert, or translocate all or part
of a chromosome. Inversions
reverse the direction of parts of
chromosomes. Translocations
happen when part of one
chromosome breaks off and
attaches to another.
Practice:
Name the mutation
1. DNA: ACC TGA GTT
mRNA: UGG ACC CAA
2.
DNA: ACC TGA GTT
mRNA: UGA GAC CCA A
3.
DNA: ACC TGA GTT
mRNA: GGA CCC AA
Down Syndrome (trisomy 21)
Kleinefelter’s Syndrome