Image from the PBS website on evolution
Mutations are very important for the evolution of a species. A mutation
is a random change in the DNA of on organism. There are several different
types of mutations.
Often when people think of a mutation they think of an oddity that inhibits
an individual. This is not always the case, not all mutations are harmful.
Some can actually benefit an individual, giving it greater fitness to survive
and reproduce in its environment. The frequency of an advantageous mutation
is likely to increase due to natural selection.
Examples of Natural Selection
Examples of Natural Selection
Types
of Mutations
1.
Point mutations- These are the most common forms of mutations.
In a point mutation, one nucleotide on a DNA segment is exchanged for another.
These may alter the expression of a gene, and thereby, produce an altered
RNA and/or protein molecule.
2. Additions/Deletions- During the copying of a DNA strand, a segment of the strand may be deleted or a new segment may be inserted. These mutations may cause frameshift mutations if the segments are misaligned.
3. Transposons- Transposons occur when genes move from one place in the genome to another.
4. Mutations from External Sources-may be caused by the following:
| a.
b.
c.
d.
|
Viruses with the ability to insert their DNA into the genome of the host (retroviruses) Plasmids
which are circular pieces of DNA that are passed form bacterium to bacterium
Parasites
which pick up genetic material from one host and carry it to the
next host.
Mutagens in the environment. These include carcinogens which cause cancer as well as teratogens which cause birth defects. |
Created by Karen
Sharrow-Reabe Dec 2001.
References