DNA-sequence ends {3' end} can have expressed sequence tags. At 3' ends, ESTs accumulate, end within 10 bases of each other, and overlap near polyadenylation consensus sequence, after coding region and before polyA terminus. 3' ends are within last 1500 bases of transcript 3'-UTR.
Nucleic acids have 5' ends {cap, nucleic acid}.
DNA sequences {cistron}, typically having several genes, can underlie biochemical functions.
Messenger RNA can be templates for single-stranded DNA synthesis {complementary DNA} (cDNA). cDNA corresponds to cell-DNA exons.
RNA {complementary RNA} (cRNA) can transcribe from single-stranded DNA.
Gene regions {exon} transcribe as mRNA sequences. Exons are not introns. Functional mRNAs have spliced exons, with intron regions removed.
Genes have regions {intron} that are not for translation. Introns can affect protein folding.
DNA sequences {open reading frame} can code for one mRNA, because they have no stop codons until end.
Poly(A) polymerase adds 100 to 300 adenosines {polyA tail} to 3' ends. Perhaps, polyA tails block RNAse.
DNA contains repetitive sequences, introns in gene-coding regions, untranslated sequences 5' and 3' to gene-coding regions, pseudogenes, and transposed regions {junk DNA} {selfish DNA}. Almost all DNA is non-coding junk DNA. Over time, species can gain and lose junk DNA.
repeats
Most junk DNA is repetitive. Species have distinctive repetitive sequences. Repetitive regions change in cancer and cell growth.
Satellite DNA has 100 bases. Minisatellite DNA, such as GGGCAGGAXG, has 10 to 20 bases, is at 1000 loci, has 5 to 50 repeats, and initiates gene swapping. Microsatellite DNA has less than 20 bases.
Alu repeats are only in primates, repeat million times in different locations, are 10% of DNA, have internal promoter, and are similar in sequence to ribosome gene.
B1 repeats are in mice.
LINE-1 repeats contain reverse transcriptase, are 15% of DNA, and have a hundred thousand copies.
introns
Humans and other highly evolved species tend to have more, longer, and more-complex introns.
untranslated regions
5' and 3' untranslated regions contain enhancers and suppressors and regulate protein translation. Humans and other highly evolved species tend to have longer and more-complex 5' and 3' untranslated regions.
transposition
Retroviruses and bacteria cause transposition. DNA transposition rate in primates is lower than in mice. Immune responses use transposition.
language
Junk DNA statistically appears to have sequence patterns with characteristics similar to patterns in language. Junk sequences can be codes for processes that control signal transmission, gene expression, protein alteration, or other processes that use information.
Many non-functional DNA regions {pseudogene} are similar in sequence to actual genes, such as ribosome genes. Reverse transcription can incorporate host or foreign mRNA into DNA {processed pseudogene} {retropseudogene}, using RNA-mediated retroposon transposition. Mutations can make pseudogenes. Pseudogenes can have copies and repeats. They can harbor RNA sequences. Pseudogenes can represent information to turn off or turn on. Species have distinctive pseudogene patterns.
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.
Genes and cistrons have control regions {operon}, where repressors bind to prevent transcription.
Genes {repressor gene} can make repressors, which bind to operator regions.
Repressors bind to operon regions {operator region} that precede coding regions.
RNA polymerase binds to regions {promoter region} just before coding regions. Repressors block RNA polymerase binding. Derepressors can bind to repressors at allosteric sites to release repressors from operators. Corepressors can bind to repressors to aid repression. Inducers can bind to repressors to block repression.
RNA-polymerase-III 50-base internal-control regions have two regions {zinc finger} that bind zinc.
Oligonucleotides {primer DNA} can start polymerization by DNA polymerase.
Repeated CGs {CpG island} can be in regulatory DNA.
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Date Modified: 2022.0225