DNA

This page is about DNA and interesting genomic phenomena.

Transposable Elements

A transposable element (TE) or transposon is a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Many TEs contain promoters which drive transcription of their own transposase. These promoters can cause aberrant expression of linked genes, causing disease or mutant phenotypes.

Retrotransposons

Retrotransposons also called transposons via RNA intermediate are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. These DNA sequences use a "copy-and-paste" mechanism, whereby they are first transcribed into RNA, then converted back into identical DNA sequences using reverse transcription, and these sequences are then inserted into the genome at target sites.

DNA Transposons

DNA Transposons (aka Class II elements) are a group of transposable elements that can move in the DNA of an organism via a single- or double-stranded DNA intermediate. There are autonomous, as well as nonautonomous DNA transposons. The latter use the enzymatic machinery of the former for their amplification in a genome. It is estimated, that there are around 300,000 copies of DNA transposon fossils in the human genome and they make up around 3% of it.

Alu element

An Alu element is a short stretch of DNA originally characterized by the action of the Arthrobacter luteus (Alu) restriction endonuclease.[1] Alu elements are the most abundant transposable elements, containing over one million copies dispersed throughout the human genome.[2] They are derived from the small cytoplasmic 7SL RNA, a component of the signal recognition particle.

Short Interspersed Nuclear Elements

Short Interspersed Nuclear Elements (SINEs) are non-autonomous, non-coding transposable elements (TEs) that are 50-500 base pairs long. The internal regions of SINEs originate from tRNA and remain highly conserved, suggesting positive pressure to preserve structure and function of SINEs. While SINEs are present in many species of vertebrates and invertebrates, SINEs are often lineage specific, making them useful markers of divergent evolution between species. Copy number variation and mutations in the SINE sequence make it possible to construct phylogenies based on differences in SINEs between species. SINEs are also implicated in certain types of genetic disease in humans and other eukaryotes.