Repeated sequence (DNA)
Encyclopedia
In the study of DNA sequence
s, one can distinguish two main types of repeated sequence:
In primates, the majority of LINEs are LINE-1 and the majority of SINEs are Alu's
.
In prokaryotes, CRISPR
are arrays of alternating repeats and spacers.
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
s, one can distinguish two main types of repeated sequence:
- Tandem repeatTandem repeatTandem repeats occur in DNA when a pattern of two or more nucleotides is repeated and the repetitions are directly adjacent to each other. -Example:An example would be:in which the sequence A-T-T-C-G is repeated three times.-Terminology:...
s:- Satellite DNASatellite DNASatellite DNA consists of very large arrays of tandemly repeating, non-coding DNA. Satellite DNA is the main component of functional centromeres, and form the main structural constituent of heterochromatin....
- MinisatelliteMinisatelliteA minisatellite is a section of DNA that consists of a short series of bases 10-60 bp. These occur at more than 1,000 locations in the human genome...
- Microsatellite
- Satellite DNA
- Interspersed repeatInterspersed repeatInterspersed repetitive DNA is found in all eukaryotic genomes. Certain classes of these sequences propagate themselves by RNA mediated transposition, and they have been called retrotransposons. Interspersed repetitive DNA elements allow new genes to evolve. They do this by uncoupling similar DNA...
s:- SINEs (Short Interspersed Nuclear Elements)
- LINEs (Long Interspersed Nuclear Elements)
In primates, the majority of LINEs are LINE-1 and the majority of SINEs are Alu's
Alu sequence
An Alu element is a short stretch of DNA originally characterized by the action of the Alu restriction endonuclease. Alu elements of different kinds occur in large numbers in primate genomes. In fact, Alu elements are the most abundant mobile elements in the human genome. They are derived from the...
.
In prokaryotes, CRISPR
CRISPR
CRISPRs are loci containing multiple short direct repeats that are found in the genomes of approximately 40% of bacteria and 90% of archaea. CRISPR functions as a prokaryotic immune system, in that it confers resistance to exogenous genetic elements such as plasmids and phages...
are arrays of alternating repeats and spacers.
Other types of repeats
Note: The following are covered in detail in "Computing for Comparative Microbial Genomics".- Direct repeatDirect repeatDirect repeats are a type of genetic sequence that consists of two or more repeats of a specific sequence.Direct repeats are nucleotide sequences present in multiple copies in the genome. There are several types of repeated sequences. Interspersed DNA repeats are copies of transposable elements...
s- Global direct repeat
- Local direct simple repeats
- Local direct repeats
- Local direct repeats with spacer
- Inverted repeatInverted repeatAn inverted repeat is a sequence of nucleotides that is the reversed complement of another sequence further downstream.For example, 5'---GACTGC....GCAGTC---3'. When no nucleotides intervene between the sequence and its downstream complement, it is called a palindrome. Inverted repeats define the...
s- Global inverted repeat
- Local inverted repeat
- Inverted repeat with spacer
- Palindromic repeat
- Mirror and everted repeats