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Mutations
 A _________________is any alteration in the nucleotide base sequence
in the DNA molecule.
Significance of Mutations
 Some mutations occur spontaneously due to random errors that occur
during___________________. More often, however, mutations are
caused by ______________________(chemicals or radiation) that
damage the DNA. When such damage occurs, if the damage is not
repaired correctly, then a mutation occurs. Mutations result in
___________________________________ within a species. Even
though mutations are rare, they are the ultimate source of
_______________________ within a species.
 One common type of mutation is the ___________________ (OR POINT
MUTATION). In a substitution, ____nucleotide base is substituted for
another in the DNA, changing the ____________of bases.

The consequences of such a mutation vary.
–
Ex. GACTGACTG
GACTGCCTG
Types of substitution mutations:
o Some amino acids have ________________word that codes for
them. In some cases, the new code word codes for the
______________amino acid as the original. This is referred to
as a _______________________mutation because even
though the DNA code has changed, there is ______________in
the ___________________sequence of the protein.
o In other cases, the new code word codes for a _________amino
acid than the original code word. When this happens the
protein coded for will have a different amino acid sequence than
the original and may or may not function properly. This type of
mutation is called a ____________________mutation.
o Occasionally, the new code word is a
_______________________codon that causes a premature
stop signal at the wrong place in the message. In this case, the
encoded protein is _________produced at all. This type of
mutation is referred to as a ____________________mutation.

Another type of mutation is the FRAMESHIFT MUTATION. In this type of
mutation, a nucleotide is either ____________or ____________ to the
strand at some point along the strand. If this occurs, ____________amino
acid from the point of the mutation will be changed.
Chromosomal Mutations
Involves changes in the _____________________of chromosomes (which are
large portions of DNA) which can cause severe deformities and many times
death.
Types of Chromosomal Mutations:
________________– part of chromosome is permanently missing
________________– part of chromosome is copied and repeated
________________– chromosome breaks off and reattaches in reverse
________________– chromosome breaks off and attaches to another
chromosome.
Exercise 5: Mutations
Use the following DNA molecule to answer the following questions.
AATGCCAGTGGTTCGCAC
1. Write the base sequence of the complementary DNA strand.
2. Using the original DNA code, write the base sequence that would appear
on an mRNA strand after transcription.
3. Determine the order of amino acids in the resulting protein fragment.
There is no start or stop in the sequence.
4. If the forth base in the original DNA strand were changed from G to C,
how would this affect the resulting protein fragment?
5. If a G were added to the original DNA strand after the third base, what
would the resulting mRNA look like?
How would this addition affect the protein? Give the sequence of amino
acids.
6. Which change in DNA was a point mutation?
Which was a frameshift mutation?
7. In what way did the point mutation affect the protein?
8. How did the frameshift mutation affect the protein?