In eukaryotes, important genes and satellite DNAs repeat {DNA repeat, genetics}. Eukaryotes have many repeated or duplicated DNA regions. Histone, rRNA, tRNA, and other genes that are fundamental to cell processes repeat many times in same chromosome regions {clustering, chromosome}.
gene duplication
Gene duplication allows variant protein forms to arise. Original gene still provides needed protein. Duplicate gene can mutate and recombine to make variant protein, such as globin chains. Duplication can revert, by gene conversion after sequence break, using normal sequence as template to repair mutant sequence.
Besides repeated and duplicated genes, eukaryote genomes have many short, often tandemly repeated sequences {single-sequence DNA} {satellite DNA} of 5 bases to 200 bases.
Yeast has retrotransposon Ty elements, which contain reverse transcriptase, whose direct repeats or long terminal repeats {delta element} have promoters.
Simple tandem repeats {simple tandem repeat} (STR) {microsatellite DNA}, like repeated CA, vary in repeat number. Mononucleotide, dinucleotide, trinucleotide, or tetranucleotide tandem repeats, such as CA dinucleotide repeats, with differing lengths, are in all chromosomes. DNA markers can have mononucleotide, dinucleotide, trinucleotide, or tetranucleotide repeats in tandem arrays, such as CA or GT dinucleotide repeats. Perhaps, they distribute throughout genomes. Microsatellites can aid genetic mapping. Simple tandem repeats can have polymorphism.
Minisatellite DNA tandem repeats {variable-number tandem repeat} (VNTR) between restriction sites {hypervariable loci} can vary in repeat length and repeat number and are useful for DNA fingerprinting. Forensics, cell cultures, and family relationship tracing can identify individuals. Large-enough polymorphism sets can provide high probabilities that identifications are unique. Myoglobin-gene introns, mitochondrial DNA, and class II HLA gene DQalpha test for polymorphisms in forensics.
Satellite DNA, found only in vertebrates, can have 130-base to 300-base repeats that are not tandem {short interspersed element} (SINE). RNA polymerase III transcribes SINEs. SINEs include Alu repeats. Human genome has one million Alu repeats. SINE-repeat sequences entered genomes by transposition.
Satellite DNA, found only in vertebrates, can have long repeats {long interspersed element} (LINE) that are not tandem. LINE repeat sequences entered genomes by transposition.
Satellite DNA {minisatellite DNA} can have 10-base to 100-base sequence that tandem repeats 20 to 50 times. In all chromosomes, 10-nucleotide tandem repeats, with differing lengths, often cluster near telomeres. Minisatellite DNAs do not transcribe. At genome locations, repeat number gradually evolves, so individuals have different repeat numbers.
uses
Minisatellite DNA can be for genetic mapping. Minisatellite DNA lengths are unique to individual and can be for identification by DNA fingerprinting.
Minisatellite DNA lengths are unique to individuals {DNA fingerprinting}, for identification. At genome locations, repeat number gradually evolves, so individuals have different repeat numbers.
4-Genetics-Nucleic Acid-Regions
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Date Modified: 2022.0225