by Tami Port MS

Created on: June 13, 2009   Last Updated: August 09, 2009

Ever wonder why your cat has six toes? Does the latest X-Men movie leave you curious about real mutants? Here's an explanation of genetic mutations; what they are and and how they occur in nature.

* The Genetic Code *

Genes are units of inheritance that exist within chromosomes; each chromosome a double-stranded molecule of DNA (deoxyribonucleic acid). Along the two strands of a DNA molecule are a series of molecular subunits called bases. This sequence of bases, the order in which they occur, is the actual genetic code.

A mutation is an alteration of a gene's normal DNA base sequence. Because genes are instructions for building protein molecules, a change in the genetic instructions can result in a critical change to the protein products of DNA. To better understand the relationship between mutations, genes, DNA and proteins, it is helpful to first review what DNA is and how it works.

* Nucleic Acids & Nucleotides *

Deoxyribonucleic acid (DNA) is the genetic material of cells. Nucleic acids are polymers (big molecules) composed of monomers (little molecules) called nucleotides. Nucleotide monomers consist of 3 portions:
1. a pentose sugar
2. one or more phosphate groups
3. one of five cyclic nitrogenous bases

* The Twisted "Ladder" of Nucleic Acid *

The nucleotides of DNA are linked together by chemical bonds between the phosphate of one nucleotide and the sugar of next, creating a phosphate-sugar backbone, with the nitrogenous bases extending from this backbone like the teeth of a comb. In all living things, DNA exists as a double-stranded molecule, with the bases from each strand attracted to each other by hydrogen bonds.

* Nucleotide Bases & the Genetic Code *

The nucleotides of DNA each contain one of four possible nitrogenous bases: Adenine (A) Cytosine (C) Guanine (G) 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 that makes each of us unique.

* Replication: Copying DNA *

Most of the cells in the human body are frequently dividing. When cells divide, a new copy of DNA must be made, so that each new cell has a complete set of genetic instructions. Sometimes, when a new DNA molecule is built, the wrong base gets inserted, or deleted, changing the genetic code. This is a type of mutation.

* Transcription & Translation: Building Proteins Based on the

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