by Tami Port MS

Created on: June 15, 2009   Last Updated: August 04, 2009

A mutation is a rare change in a gene's DNA sequence. The result of these genetic mistakes can range from no effect on the organism to the production a defective cellular protein that may have disastrous implications.

Deoxyribonucleic acid (DNA), is the genetic material of cells; the organic molecule of genes and the chromosomes that genes are part of. Nucleic acids are polymers (big molecules) built from monomers (little molecules) called nucleotides. In order to understand what a mutation is, it helps to know a little about the structure of DNA's building blocks, nucleotide.

DNA's nucleotide monomers consist of 3 portions:
1. a pentose sugar
2. one or more phosphate groups
3. one of four cyclic nitrogenous bases

* Nucleotide Bases & the Genetic Code *

The nucleotides of DNA each contain one of four possible nitrogenous bases:

Purines (double-ring bases):

* Adenine (A)
* Guanine (G)

Pyrimidines (single-ring bases):

* Cytosine (C)
* Thymine (T)

The specific base is the only thing that makes one nucleotide differ from another. When nucleotides exist together in a nucleic acid, such as the DNA of our genome, the sequence of these bases is actually the genetic code making each of us unique.

* DNA Replication: Copying DNA *

Most of the cells in our bodies are frequently dividing, creating new cells. When cells divide, a new copy of DNA must be made, so that each new cell has a complete set of genetic instructions.

* Translation: Making Proteins *

Translation is the process in which the nucleic acid blueprint is read and the information used to build a protein molecule. Each group of three nucleotides in the genetic blueprint is called a codon and encodes for one amino acid. In other words, our cells read the nucleic acid triplet code and build proteins based on the 3-nucleotide "words".

* DNA and Mutations *

Very rarely, when a new DNA molecule is being built, the wrong nucleotide base is inserted. This is a mutation. Some mutations are large-scale and can involved large chromosomal sections or entire genes. Other mutations are considered small-scale, only affecting one or a few nucleotides. Small mutations may or may not cause a problem with the DNA blueprint being translated. The following are different types of small-scale mutations:

* Point Mutations *

Point mutations involve the exchange a single nucleotide for another; most typically a purine for a purine (A switch with G) or a pyrimidine for a pyrimidine, (C switched with T). A similar, but less common mistake

• 1
• 2
• Next Page >>