Difference Between VNTR and STR

Main Difference – VNTR vs STR

Repetitive DNA is the patterns of nucleic acids that occur in multiple copies throughout the genome. They make up major proportions of the nuclear DNA in eukaryotes. Tandem repeats are one of the major types of repetitive DNA that copy repetitive sequence units that lie adjacent to each other, forming a nucleotide block. VNTR (variable number tandem repeats) and STR (short tandem repeats) are two types of tandem repeats found in the eukaryotic genome. VNTR is a type of minisatellite DNA whereas STR is a type of microsatellite DNA. The main difference between VNTR and STR is that the repetitive unit of VNTR is 10-60 base pairs whereas the repetitive unit of STR is 2-6 base pairs.

Key Areas Covered

1. What is VNTR
– Definition, Features, Importance
2. What is STR
– Definition, Characteristics, Importance
3. What are the Similarities Between VNTR and STR
– Outline of Common Features
4. What is the Difference Between VNTR and STR
– Comparison of Key Differences

Key Terms: Forensic Genetics, Microsatellite, Minisatellite, Repeating Nucleotide Units, STR, Tandem Repeats, VNTR

What is VNTR

VNTR refers to a type of tandem repeats in which a short sequence of nucleotides (10-60 base pairs) are repeated a variable number of times in a particular locus. Therefore, VNTR is also known as minisatellites. VNTRs are interspersed throughout the chromosomes of the eukaryotic genome. Generally, the number of repeated units in a VNTR vary between individuals. Hence, the length of the array formed by VNTRs also varies between individuals. As the variant number of chromosomes are inherited from parents, they can be used in the parental or personal identification. The variation of VNTRs in six individuals are shown in figure 1.

Figure 1: VNTR Variation in Individuals

VNTRs are the first types of polymorphisms used in DNA profiling to determine the DNA characteristics of a particular person. They are also used as genetic markers in RFLP (restriction fragment length polymorphism), a technique that uses PCR, gel electrophoresis, and production of band patterns by southern blotting.

What is STR

STR refers to a type of tandem repeats in which a short sequence of nucleotides (2-6 base pairs) are repeated a variable number of times in a particular locus. STRs are a type of microsatellites, and they are also known as short sequence repeats (SSRs) in plant genetics. The repeating units composed of a single nucleotide are known as single nucleotide polymorphism (SNP). STRs are the commonest type of genetic polymorphisms analyzed currently in forensic genetics. DNA profiling with the use of STRs as genetic markers is shown in figure 2.

Figure 2: DNA Profiling

Mutations in some of the STR regions lead to genetic diseases such as fragile X syndrome and Huntington’s disease.

Similarities Between VNTR and STR

VNTR and STR are two types of tandem repeats.
Both VNTR and STR are structural regions of the eukaryotic genome.
Both VNTR and STR consist of noncoding DNA.
BothVNTR and STR are inherited from parents.
Both VNTR and STR are composed of repetitive sequences, arranging adjacent to each other in an array.
Both VNTR and STR produce genetic polymorphism.
Both VNTR and STR are spread throughout the genome.
Both VNTR and STR are used as genetic markers in forensic genetics.
Mutations in both VNTR and STR lead to genetic diseases.

Definition

VNTR: VNTR is a type of tandem repeat in which a short sequence of nucleotides (10-60 base pairs) are repeated a variable number of times in a particular locus.

STR: STR is a type of tandem repeat in which a short sequence of nucleotides (2-6 base pairs) are repeated a variable number of times in a particular locus.

Number of Repeating Nucleotides

VNTR: VNTR consists of 10-60 base pairs.

STR: STR consists of 2-6 base pairs.

Type of Repetitive DNA

VNTR: VNTR is a type of minisatellite DNA.

STR: STR is a type of microsatellite DNA.

Number of Repeats

VNTR: VNTR consists of 10-1,500 repeats in the array.

STR: STR consists of 5-200 repeats in the array.

Size of the Array

VNTR: VNTR forms an array of 0.5-15 kb.

STR: STR forms an array of 10-1000 bp.

Complexity of the Array

VNTR: VNTR produces heterogeneous arrays.

STR: STR produces homogenous arrays.

Conclusion

VNTR and STR are two types of tandem repeats that form arrays of adjacent repetitive units in the eukaryotic genome. VNTR consists of comparatively a long repeating units of nucleotides (10-60 base pairs). STR consists of short repeating units of nucleotides (2-6 bp). The main difference between VNTR and STR is the length of the repeating units of each type of tandem repeats.

Reference:

1. “Variable number tandem repeat.” ScienceDirect Topics, Available here.
2. “The Science of Forensic Genetics.” CRG – Council for Responsible Genetics, Available here.

Image Courtesy:

1. “D1S80Demo” By PaleWhaleGail at English Wikipedia (CC BY-SA 3.0 ) via Commons Wikimedia
2. “Stages of Gene Fingerprinting” By Sneptunebear16 – Own work (CC BY-SA 4.0) via Commons Wikimedia