Mammalian-wide interspersed repeats (MIRs) are

transposable elements A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Trans ...

in the genomes of some organisms and belong to the group of Short interspersed nuclear elements (SINEs).

Incidence

MIRs are found in all mammals (including

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...

s).

In human

It is estimated that there are around 368,000 MIRs in the

human genome The human genome is a complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual mitochondria. These are usually treated separately as the ...

Structure

The MIR consensus sequence is 260 basepairs long and has an A/T-rich 3' end.

Propagation

Like other Short interspersed nuclear elements (SINEs), MIR elements used the machinery of LINE elements for their propagation in the genome, which took place around 130 million years ago. They cannot retrotranspose anymore since the loss of activity of the required reverse transcriptase.

History of discovery

MIR elements have been first described in human genome 1989-1991 and were first referred as MB1 family repeats (mirror to sequences of mouse B1 repeat). Then this family repeats were found in other mammalian genomes. Then this family was renamed as "Mammalian interspersed repeats" in 1992 Later this family was shown to be common for vertebrate genomes.

References

{{Repeated sequence Mobile genetic elements Molecular biology