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Encyclopedia > Alu sequence

An Alu sequence is a short stretch of DNA originally characterized by the action of the Alu restriction endonuclease. Alu sequences of different kinds occur in large numbers in primate genomes. In fact, Alu sequences are the most abundant mobile elements in the human genome. They are derived from the small cytoplasmic 7SL RNA, a component of the signal recognition particle. The event, when a copy of the 7SL RNA became a precursor of the Alu sequence, took place in the genome of an ancestor of Supraprimates[1]. The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A restriction enzyme (or restriction endonuclease) is an enzyme that cuts double-stranded DNA. The enzyme makes two incisions, one through each of the sugar-phosphate backbones (i. ... Endonucleases are enzymes that cleave the phosphodiester bond within a nucleotide chain. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... The signal recognition particle (SRP) is a protein-RNA complex that recognizes and transports specific proteins to the endoplasmic reticulum in eukaryotes and the plasma membrane in prokaryotes. ... Orders Glires Rodentia Lagomorpha Euarchonta Dermoptera Scandentia Primates The Euarchontoglires (synonymous with Supraprimates) are a mammalian superorder based on molecular genetic sequence analyses and Retrotransposon presence/absence data, combining the Glires clade, which consists of the Rodentia and the Lagomorpha, with that of the Euarchonta, a clade consisting of the...


Alu insertions have been implicated in several inherited human diseases, including various forms of cancer, as discussed later in this article.


The study of Alu sequences has also been important in elucidating human population genetics and the evolution of primates, including the evolution of humans. The Alu endonuclease is so-named because it was isolated from Arthrobacter luteus. Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. ... This article is about evolution in biology. ... Families 15, See classification A primate is any member of the biological order Primates, the group that contains all the species commonly related to the lemurs, monkeys, and apes, with the latter category including humans. ... // For the history of humans on Earth, see History of the world. ...


The Alu family

The Alu family is a family of polymorphisms in the Human genome. Alu sequences are about 300 base pairs long and are therefore classified as short interspersed nuclear elements (SINEs) amongst the class of repetitive DNA elements. In biology, polymorphism can be defined as the occurrence in the same habitat of two or more forms of a trait in such frequencies that the rarer cannot be maintained by recurrent mutation alone. ... Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin: wise man or knowing man) in the family Hominidae (the great apes). ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Base pairs, of a DNA molecule. ... SINEs are present in great numbers in many eukaryote genomes. ...


There are over one million Alu sequences interspersed throughout the human genome, and it is estimated that about 10% of the mass of the human genome consists of Alu sequences. However less than 0.5% are polymorphic [2] In biology, polymorphism can be defined as the occurrence in the same habitat of two or more forms of a trait in such frequencies that the rarer cannot be maintained by recurrent mutation alone. ...


The recognition sequence of the Alu endonuclease is 5' AG/CT 3'; that is, the enzyme splits the DNA segment between the guanine and cytosine residues. Guanine is one of the five main nucleobases found in the nucleic acids DNA and RNA; the others being adenine, cytosine, thymine, and uracil. ... Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at...


Alu sequences are retrotransposons and look like DNA copies made from RNA polymerase III-encoded RNAs. Retrotransposons are genetic elements than can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. ...


Alu sequences in primates form a fossil record that is relatively easy to decipher because Alu sequence insertion events have a characteristic signature that is both easy to read and faithfully recorded in the genome from generation to generation. The study of Alu sequences thus reveals details of ancestry because individuals will only share a particular Alu sequence insertion if they have a common sexual ancestor.


Most human Alu sequence insertions can be found in the corresponding positions in the genomes of other primates, but about 7,000 Alu insertions are unique to humans[3].


The sequence known as Alu PV92, located in Chromosome 16, can either be present or absent (although the majority of people don't have the sequence), leading to three different genotypes: Chromosome 16 is one of the 23 pairs of chromosomes in humans. ... This article does not cite its references or sources. ...

  • Presence, Presence
  • Presence, Absence
  • Absence, Absence

Alu insertions and human disease

Alu insertions are sometimes disruptive and can result in inherited disorders.However, most Alu insertions act like markers since they may segregate with a diseased allele, but the presence of the Alu does not mean that the person will definitely get the disease.


The first report of Alu-mediated recombination causing a prevalent, inherited predisposition to cancer was a 1995 report about hereditary nonpolyposis colorectal cancer [4]. Recombination usually refers to the biological process of genetic recombination and meiosis, a genetic event that occurs during the formation of sperm and egg cells. ... Year 1995 (MCMXCV) was a common year starting on Sunday (link will display full 1995 Gregorian calendar). ... Colorectal cancer, also called colon cancer or bowel cancer, includes cancerous growths in the colon, rectum and appendix. ...


In the review article referenced below [5], the authors report that the following human diseases have been linked with Alu insertions:

Breast cancer is cancer of breast tissue. ... X-Ray of a child with Ewings sarcoma of the tibia Ewings sarcoma is the common name for primitive neuroectodermal tumor. ... In medicine, familial hypercholesterolemia is a rare disease characterised by very high LDL cholesterol and early cardiovascular disease running in families. ... Haemophilia or hemophilia is the name of any of several hereditary genetic illnesses that impair the bodys ability to control bleeding. ... Neurofibromatosis is an autosomal dominant genetic disorder. ... For the disease characterized by excretion of large amounts of very dilute urine, see diabetes insipidus. ...

References

  1. ^ Jan Ole Kriegs, Gennady Churakov, Jerzy Jurka, Jürgen Brosius, and Jürgen Schmitz (2007) Evolutionary history of 7SL RNA-derived SINEs in Supraprimates. Trends in Genetics 23 (4): 158-161 [1]
  2. ^ A. Roy-Engel et al. Alu Insertion Polymorphisms for the Study of Human Genomic Diversity. Genetics 159: 279–290 (September 2001).
  3. ^ Chimpanzee Sequencing and Analysis Consortium. Initial sequence of the chimpanzee genome and comparison with the human genome. Nature 437: 69-87 (September 1 2005)
  4. ^ M. Nystrom-Lahti et al. Founding mutations and Alu-mediated recombination in hereditary colon cancer. Nat Med. 1995 Nov;1(11):1203-6
  5. ^ M. A. Batzer and P. L. Deininger. Alu Repeats and Human Genomic Diversity. Nature Reviews: Genetics 3: 370-9 (May 2002)

  Results from FactBites:
 
Alu sequence: Information from Answers.com (466 words)
The Alu endonuclease is so-named because it was isolated from Arthrobacter luteus.
The recognition sequence of the Alu endonuclease is 5' AG/CT 3'; that is, the enzyme splits the DNA segment between the guanine and cytosine.
Alu sequences in primates form a fossil record that is relatively easy to decipher because Alu sequence insertion events have a characteristic signature that is both easy to read and faithfully recorded in the genome from generation to generation.
Arithmetic logic unit - Wikipedia, the free encyclopedia (1082 words)
A typical schematic symbol for an ALU: A and B are operands; R is the output; F is the input from the Control Unit; D is an output status
ALUs for each one of these numeric systems had different designs, and that influenced the current preference for two's complement, as this is the representation that makes it easier for the ALUs to calculate additions and subtractions.
The inputs to the ALU are the data to be operated on (called operands) and a code from the control unit indicating which operation to perform.
  More results at FactBites »

 
 

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