Mutations
EQ: What is a mutation and what causes them? Are all
mutations harmful? What are two types of mutations and
what are their effects?
 A mutation is a change in the DNA; more specifically, a
change in the base sequence of the nucleotides.
- Many mutations are not harmful. Most have no effect;
some are beneficial if they spread through the population
(via reproduction of the mutated organism.)
 Mutagens – Factors in the environment that cause
mutations. For example:
1. Ultraviolet light (UV) – Sun
2. Radiation – X-Ray
3. Smoke – tobacco, pollutants
4. Chemical – cleaning supplies, pesticides
 Mutations in two cell types:
1. Somatic/autosomal mutations (are in body cells) – may
just affect that one cell.
2. Gamete mutations (sperm and egg) – may lead to death
of the developing fetus.
 Types of mutations:
There are many types of mutations; we will cover two.
1.
Point mutation – only one base is replaced in a gene.
This may or may not be harmful when making
proteins. It could be harmful if a base change creates
a different codon that codes for a different amino
acid.
2.
Frameshift mutation (Addition/Deletion) – The loss or
addition of a base in DNA. This is always deadly if it
happens in a developing fetus.
Now, try a frameshift mutation using the same DNA
strand we wrote for the point mutation. Delete a base,
and shift all the bases, from that point on, over to fill
the spot of the deleted base. mRNA will copy this new,
mutated strand. Look up the a.a. on the codon chart.
You will notice that all the amino acids from the point
of the deletion are all incorrect!