Genomic mapping database

Human genome sequence and developing model organisms to study human genome are recent advances of bioinformatics. Sequencing DNA and mapping of genome are two different units. However, DNA sequencing helps in mapping of human genome. It depends on genome markers which are developed by clone or statistical approach. Genome precursor acts as a precursor to annotate DNA sequence of the whole genome. One such technique had helped in mapping of human genome in the year 2002 and that for mouse in the year 2005. With this kick off, other lower eukaryotes and mammalian genomes were mapped. Genome mapping helps in chromosome mapping as well.

Elements of genomic map

Elements which help in mapping of human genome are as follows.

• DNA markers
• Polymorphic markers
• DNA clones

DNA markers:

A segment of DNA that can be identified is DNA marker. There are about 300-400 nucleotide bases in its length. Some are polymorphic and some are monomorphic markers. Markers are easily detected by hybridization technique or PCR analysis. Sequence tagged sites or PCR based markers can amplify DNA segments with the help of PCR. This helps physical mapping of genome.

Polymorphic markers:

Individuals’ genetic variation and genetic linkage can be predicted easily. Degree of polymorphism refers to number of alleles. Types of polymorphic markers are

• RFLP (Restriction Fragment Length Polymorphism)
• VNTR (Variable Number Tandem Repeat)
• Microsatellites
• SSLP (Short Sequence Length Polymorphism)
• STR (Short Tandem Repeats)
• STR polymorphism
• SNP (Single Nucleotide Polymorphism)

DNA clones: Cloning vehicles help in mapping of eukaryotic genome. Major types of DNA cloning are sequence tagged clones and DNA fingerprinting.

• Yeast Artificial Chromosome (YAC) is the first generated cloning library of maximum of 2 Mb nucleotide base.
• Bacterial artificial chromosome (BAC) is second generation.
• P1 artificial chromosome (PAC)

Types of maps

Genome mapping developed with the help of computational molecular biology are as follows.

• Cytogenetic map
• Genetic linkage map
• Radiation hybrid map
• Transcript map
• Physical map
• Comparative map
• Integrated map