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VNTR stands for Variable Number of Tandem Repeats. It is a region in which a short nucleotide sequence in a genome is arranged as a tandem repeat. VNTR is used in DNA Fingerprinting, forensic sciences and other genetic and biological research.
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Keyterms: VNTR, Variable Number, Tandem Repeats, Nucleotide, DNA Fingerprinting, DNA, mRNA, DNA, tRNA, Proteins, Chromosome, Genome
VNTR
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A variable number of tandem repeat (or VNTR) is a genomic region in which a short nucleotide sequence is arranged as a tandem repeat. These are present on a variety of chromosomes and can vary in length from person to person. Each variation functions as an inherited allele, allowing them to be used to identify individuals or parents.
The findings of VNTR are useful in Genetics and biology research, forensics, and DNA fingerprinting. Some VNTR sequences play important roles in transcription control, and some may also affect the translational efficiency or stability of mRNA, or modify the activity of proteins by changing their structure. The probability that these tandemly-repeated genomic regions are of physiological and biological relevance has been confirmed by certain apparent correlations of VNTR sequences with personality traits or illness.
Read Also: Bioinformatics
Types of VNTR
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Satellite
These DNA sequences are very repetitive, with each one including thousands of base pairs. Up to 100 million base pairs can be measured by a satellite. The base pairs are found in the heterochromatin sections of the genome. The Y chromosome has satellites in a great quantity. This is useful for researchers who are studying paternal genetic transmission in animals.
Minisatellite
Each repeat in a minisatellite might range from 9 to 100 base pairs. It consists of a series of tandem repeats ranging in length from 500 to 300,000 base pairs. Minisatellites have been linked to gene regulation, imprinting, and chromosomal fragile spots, etc. These are the most important aspects of the human genome. They are the first multiallelic and highly polymorphic markers for linkage studies. The majority of the minisatellites have a high GC content and have a strong strand symmetry.
Microsatellite
In microsatellites, the repeats are relatively small, ranging from 2 to 6 base pairs. The array's length varies between 10,000 and 100,000 base pairs. Short tandem repeats or simple sequence repetitions are the terms used to describe them. They are mostly present in insect and plant chromosomes, as well as vertebrate euchromatin areas.
Read Also: DNA Packaging
Importance of VNTR
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- VNTRs are the major source of RFLP genetic markers used in diploid genome linkage analysis.
- The VNTRs create a banding pattern that is unique for each individual.
- The gene VNTR is used in forensic science, DNA fingerprinting, and other genetics and biological studies.
Read more:
| Ralated Topics | ||
|---|---|---|
| Genome | DNA Replication | Human Genome Project |
| Lac Operon | Structure of RNA | Transcription |
Things to Remember
- Variable Number of Tandem Repeat (VNTR) locus are chromosomal areas in which a short DNA sequence is repeated end-to-end at a single site.
- In many species, variable number tandem repeats (VNTRs) are responsible for considerable genetic diversity.
- VNTRs have been implicated in both Mendelian and complex diseases in humans.
- VNTRs are a major source of RFLP genetic markers utilised in diploid genome linkage analysis.
- VNTRs are important in forensic crime investigations as many genomes have been sequenced.
- VNTRs are all minisatellites, but all minisatellites are not VNTRs.
- Short tandem repeats or simple sequence repetitions are the terms used to describe microsatellites.
- The satellite DNA sequences are very repetitive, with each one including thousands of base pairs.
Sample Questions
Ques: Write the full form of VNTR. How is VNTR different from a probe? (All India 2011, 1 Mark)
Ans: VNTR stands for Variable Number of Tandem Repeat.
VNTR is a class of satellite DNA in which a small sequence is arranged randomly in many repeated units whereas Probe is a radio labelled VNTR which is used for hybridization with DNA segments.
Ques: Where does a person's VNTR come from? (1 Mark)
Ans: The VNTRs are derived from the genetic information provided by the parents. They are passed down from one generation to another generation either from the mother or the father, or both.
Ques: How is a VNTR different from STR? (1 Mark)
Ans: VNTR and STR are the two types of tandem repeats that are found in a eukaryotic genome. They can be differentiated from each other on the basis of their base pairs. The repetitive unit of VNTR is 10-60 base pairs and that of STR is 2-6 base pairs.
Ques: What are the applications of VNTRs? (2 Marks)
Ans: VNTRs are a significant source of RFLP genetic markers for diploid genome linkage research. VNTR analysis is used to investigate wild and domestic animal genetic diversity and breeding trends. They are also used to differentiate bacterial pathogen strains.
Ques: What are VNTRs? Explain in detail. (2 Marks)
Ans: VNTR stands for 'Variable Number of Tandem Repeats,' which is a type of genetic marker. A variable number tandem repeat (or VNTR) is a genomic region in which a short nucleotide sequence is arranged as a tandem repeat. These can be present on a variety of chromosomes and can vary in length from person to person. This mostly occurs due to a replication error called replication slippage. Because everyone's DNA is different, researchers look at the amount of tandem repeats to figure out who they are.
Ques: What is relationship of VNTR to other types of repetitive DNA (2 Marks)
Ans: Using restriction enzymes, it was discovered that certain repetitive blocks were scattered around the genome. According to DNA sequencing, other repetitions are concentrated at certain places with tandem repeats being more frequent than inverted repeats. This may also interfere with DNA replication. VNTRs are a type of clustered tandem repeat that can vary in length due to allelic variation.
Ques: .(i) Explain DNA polymorphism as the basis of genetic mapping of the human genome.
(ii) State the role of VNTR in DNA fingerprinting. (All India 2013, 2 Marks)
Ans: (i) The methods of Human Genome Project (HGP) are focused on two main lines, i.e. expressed sequence tags and sequence annotation. By collecting information about certain repetitive DNA sequences and DNA polymorphism, the genetic and physical maps of the genome can be constructed.
(ii) Variable Number of Tandem Repeats (VNTRs) are a type of satellite DNA called minisatellite. In DNA fingerprinting, the number of tandem repeats and its size are counted.
Ques: Explain the steps of DNA fingerprinting that will help in processing of the two blood samples ‘A’ and ‘B’ picked up from the crime scene. (Foreign 2009, 3 Marks)
Ans: The technique which helps in solving a case of paternity dispute over the custody of a child by two families is called DNA fingerprinting. VNTR plays an important role in DNA fingerprinting.
Procedure of DNA fingerprinting.
(i) The repeats of VNTR show a high degree of polymorphism.
(ii) After hybridisation with the radiolabeled VNTR probe, bands of various sizes are formed.
(iii) These bands form different patterns, which vary from person to person.
(iv) The patterns developed by sample A and B, can confirm whether they belong to one person or two different persons.
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