VNTRs and Their Classification

• VNTR: 

• Repetitive DNA composed of copies of a short sequence ( DNA motif) is called as VNTR or Variable Number of Tandem Repeats.
      Its a location in a genome where a short nucleotide sequence is organised in a tandem repeat.

• Classification of VNTRs:
• VNTRs can be classified into two types, microsatellite and minisatellite. 

• 1) Microsatellite: It is a tract of repetitive DNA where certain sequences are repeated. Its characteristics are as follows,
  
  i) Microsatellites are less than 1 Kbp in length usually less than 150bp.
  ii) A typical microsatellite consists of 10-100 times repeated DNA motifs that are usually 2,3 or 4 nucleotides long.
  iii) Nucleotide repeats are very frequent in human and other genomes.
  iv) The majority of microsatellite occur in the introns and other non coding regions of the genome.
  v) Microsatellites are often found in the transcription units. They often disrupts the protein synthesis leading to diseases like myotonic dystrophy.
• 2) Minisatellites:
  
  i) Relatively larger than the microsatellites.
  ii) They are usually 1-5 Kbp in length and composed of a short DNA motif having 10-60 base pairs.
  iii) At present approximately 300 human minisatellites families have been typed.