Tandem repeat sequences

Tandem repeat sequences are a pattern of nucleotide sequences that are repeated in a direct, head-to-tail manner in the DNA. These sequences can range from a single base pair to large segments of DNA, and can be found in both coding and non-coding regions of the genome. They play a significant role in various biological processes and have been associated with numerous genetic diseases.

Structure and Types

Tandem repeat sequences are categorized based on the length of the repeating unit. The main types include:

• Microsatellites or Short Tandem Repeats (STRs): These consist of repeating units of 1-6 base pairs. They are highly polymorphic and are commonly used in DNA fingerprinting and forensic genetics.

• Minisatellites or Variable Number Tandem Repeats (VNTRs): These have repeating units of about 10-60 base pairs. They are also polymorphic and have been used in genetic linkage analysis and population genetics studies.

• Satellite DNA: This consists of larger repeating units, often hundreds or thousands of base pairs long. Satellite DNA is usually found in heterochromatic regions of the genome.

Function and Significance

Tandem repeat sequences have various functions in the genome. They can influence the structure of chromosomes, affect gene expression, and play a role in DNA replication and recombination. They also contribute to genetic diversity and evolution.

In addition, changes in the number of tandem repeats, known as copy number variations, can lead to genetic diseases. For example, expansion of trinucleotide repeats is associated with disorders such as Huntington's disease and Fragile X syndrome.

See Also

• DNA sequencing
• Genetic variation
• Molecular genetics