Download Mutations 2016

Mutations
(Section 17-5)
Now, that you know how gene
expression works, let’s see how
changes in the gene affect how
the protein is made.
Mutations - changes in DNA
• Small scale (genes) , large scale (chromosomes)
• Basic types:
– Substitutions (point mutations)
– Insertions
– Deletions
• Possible resulting effects from a mutation:
– Silent mutation
– Missense mutation
– Nonsense mutation
– Frameshift mutation
Substitutions
• Single nucleotide change.
• Possible results:
– Silent mutation
• no amino acid change
• redundancy in code
– Missense mutaion
• change amino acid
• Changes the final protein
– Nonsense mutation
• change to stop codon
• Stopping prematurely
Point mutation leads to Sickle cell anemia
What kind of mutation?
Insertions or
Deletions
• Adding a nucleotide
• Deleting a nucleotide
• Results:
– Frameshift mutation – a
change every amino acid
from where the
mutation occurred
Where would this mutation
cause the most change:
beginning or end of gene?
What’s the value of
mutations?
A part of an mRNA molecule with the following sequence is
being read by a ribosome: 5' CCG-ACG 3' (mRNA). The
following activated transfer RNA molecules are
available. Two of them can correctly match the mRNA
so that a dipeptide can form.
tRNA Anticodon
Amino Acid
GGC
CGU
UGC
Proline
Alanine
Threonine
CCG
ACG
Glycine
Cysteine
CGG
Alanine
The dipeptide that
will form will be
A.
B.
C.
D.
E.
cysteine-alanine.
proline-threonine.
glycine-cysteine.
alanine-alanine.
threonine-glycine.