Why Genome mapping?
Genomes are intricate, composed as they are of millions of base pairs. And finding your way around a human genome or a viral genome to look for a specific gene of interest is tricky to say the least. So you need a map, a way of pointing out where specific landmarks, such as genes, are located. Genome mapping techniques determine the location and order of specific genes on a particular region of a chromosome. They also establish the relative distance between genes.
Once the chromosomal regions have been mapped, it becomes easier to carry out DNA sequencing. Genome mapping provides a guide for sequencing experiments by showing the locations of genes as well as other distinguishing genomic features. To stay with our map analogy you can think of it like this; a genome map presents the gross picture, it identifies specific landmarks in a genome such as genes – much like a road map highlights points of interest such as monuments and churches. DNA sequencing is a more sophisticated map if you like, and provides even more detail by spelling out the exact order of bases in a particular region of DNA.
A genome map is the first step toward finding a particular gene of interest, and it shows the arrangement of genes and genetic markers along the chromosomes. It offers hints as to where on a chromosome a gene may be located. If a child has inherited a disease from a parent a genome map can tell you if it was transmitted via one or more genes, and the Cystic fibrosis gene and muscular dystrophy gene were both located via genome maps.
In humans a genome map is constructed from DNA that’s been isolated from a blood or a tissue sample.
A genetic map helps to find genetic landmarks known as genetic markers. Markers can be regions of DNA that do not contain genes or they can be located within genes that code for a particular trait such as hair color, or eye color. Whichever kind of marker it is, you’ll find that it is usually associated with a particular region of a chromosome, and so it is hopefully pointing scientists in the right direction of the gene they are looking for.
A genetic marker refers to any noticeable variation resulting from an alteration, or mutation at a single genetic loci. Some of the most commonly used DNA markers are RFLPs, or Restriction Fragment Length Polymorphisms, VNTRs or, Variable Number of Tandem Repeat Polymorphisms, Microsatellite polymorphisms, and SNPs: Single Nucleotide Polymorphisms.
Speedy Map Reading
When genome maps are combined with physical maps and rapid DNA sequencing technologies, they drastically reduce the time it takes to find a gene. The process once took years, but a gene can now be identified in a matter of months, sometimes weeks, and it is revolutionizing the biotech industries.
NCBI. “Genome mapping: A Guide to the genetic highway we call the human genome,” retrieved on July 1, 2009 from Genome Mapping.