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Mysteries hidden in the genes: How do VNTRs reveal the secrets of individual identity?
Genes play a vital role in the mysteries of life. Variable Number Tandem Repeat (VNTR) is a sequence that is commonly found in the genome. The number of repetitions of these sequences varies between individuals, making them a key tool for individual identification. This article will explore in depth the structure and inheritance of VNTRs and their applications in scientific research and forensics, and inspire our imagination of genetic diversity.
The variability of VNTR makes it an indispensable part of criminal investigations.
Structure and variation of VNTR
The short nucleotide sequences in VNTRs are arranged in tandem repeats, and these repeat units often show length variation at different locations on the chromosome. Each of these variant VNTRs can be considered a genetic allele, which is why they are widely used for individual or parentage identification. Repeat sequences are usually isolated using restriction enzymes and polymerase chain reaction (PCR), and their size can be determined by gel electrophoresis.
Isolation of VNTRs from surrounding DNA by PCR or RFLP can produce a banding pattern that is unique to each individual.
Application in genetic analysis
VNTR was once an important RFLP gene marker used in diploid genome linkage analysis (mapping). With the complete sequencing of the genome, VNTRs have become the cornerstone of DNA fingerprinting in forensic crime investigations. When testing a group of independent VNTR markers, the probability of two unrelated individuals having the same allele pattern is extremely low. In addition, VNTR analysis has been used to study genetic diversity and reproductive patterns in populations of wild or domesticated animals.
VNTRs can be used to clearly distinguish between individual strains of bacterial pathogens.
Inheritance in Genetics
Two basic genetics principles can be applied in the analysis of VNTR data: identity matching and genetic matching. Identity matching requires that the VNTR alleles from a specific location must match; whereas genetic matching requires that the VNTR alleles follow the laws of inheritance. In the case of matching an individual with their parents or children, there must be one allele that matches each parent. In the case of more distant relationships, such as grandparents or siblings, the match must be consistent with the degree of relatedness.
Relationship to other repetitive DNA types
Repetitive DNA makes up more than 40% of the human genome and is arranged in an intricate pattern. Through the use of restriction enzymes, scientists discovered that some repeat blocks are interspersed in the genome and are not all arranged in tandem. Subsequent DNA sequencing revealed that certain repeats were clustered at specific locations and that tandem repeats were more common than inverted repeats. VNTRs are just such tandem repeat segments that exhibit length variation.
While all VNTRs are minisatellites, not all minisatellites are VNTRs.
Various types of VNTR
VNTRs are minisatellites in which the repeat sequence is typically ten to one hundred base pairs in size. Minisatellites are special tandem repeat sequences of DNA in which repeated sequences are directly followed by other repeated sequences. Because the repeat sequence of VNTRs ranges from ten to one hundred bases and each repeat sequence is exactly the same, they are considered a type of minisatellite. While VNTRs have variation, some non-VNTR minisatellites routinely display a fixed number of repeats.
Conclusion
With the advancement of science, VNTR not only has important practical value in forensic medicine, but also allows us to have a deeper understanding of genetics. The repetitive sequences hidden in this gene reflect the uniqueness and diversity of each individual. Just as VNTR opens the door to the mystery of the genome for us, how will other unknown genetic mysteries affect our existence?
