Within a gene, there are “repeat regions” (repeated sequences) in which the same sequence is repeated. Although these regions do not encode proteins, they play important roles in genome structure and evolution, as well as in the regulation of gene expression. There are several types of repeat regions, each with different characteristics and functions.
Major Repeat Region Types
- Satellite DNA
- Characteristics: A long sequence of several hundred to several thousand base pairs repeated. It is particularly abundant at the center (centromere) and ends (telomere) of chromosomes.
- Role: Involved in maintaining chromosome structure, contributing to chromosome segregation at the centromere and ensuring chromosome stability at the telomere.
- Minisatellite
- Characteristics: Short sequences of 10 to 60 bases are repeated tens to hundreds of times.
- Role: Because each individual has a different pattern of repeats, they are used for personal identification such as DNA fingerprinting. It plays a particularly important role in forensic science and paternity testing.
- Microsatellite (short repeat sequence, STR)
- Characteristics: Very short sequences of 2 to 6 bases repeated several to dozens of times.
- Role: They are useful in the study of evolution and adaptation because they create diversity within the genome. In addition, since each individual has a different pattern, they are used for personal identification and parent-child identification as well as minisatellites.
- Transposons (jumping genes)
- Characteristics: A sequence that has the property of moving within DNA, and there are different types such as “LINE” and “SINE”.
- Role: By changing their position in the genome, they can cause mutations and are a source of genetic diversity in the evolutionary process. It is also said that genomic regions containing large amounts of transposons account for about 40% of the total genome
Role and significance of repeat regions
- Genetic diversity: Variation in the number of repeats in repeat regions generates genomic diversity and contributes to evolution.
- Chromosome stability: The presence of repeat regions at specific sites, such as centromeres and telomeres, serves to stabilize the structure of chromosomes.
- Genetic disease: Excessive amplification of repeat regions can cause certain genetic diseases. For example, Huntington’s disease and other genetic diseases are caused by an abnormal increase in specific repeat sequences.
Summary
Repeat regions are repeating sequences in DNA that play an important role in genome structure, genetic diversity, and chromosome stability. Repeat regions provide genetic diversity in evolution and adaptation, and also aid in personal identification, forensic medicine, and even genetic disease research.
