Transposons

Definition

Transposons are DNA fragments that are capable of moving from one place to an other of a cells genome.

Frequency

The frequency of transposable elements in different genomes is listed in the following table [1].

		Genome size	% transposons
Rana esculenta	Frog	5.6–8.0	77
Zea mays	Maize	5.0	60
Homo sapiens	Human	3.5	45
Mus musculus	Mouse	3.4	40
Drosophila melanogaster	Fruitfly	0.18	15–22
Caenorhabditis elegans	Worm	0.1	12
Saccharomyces cerevisiae	Yeast	0.012	3–5
Escherichia coli	Bacteria	0.0046	0.3

Interestingly there is no rule such as the higher evolved an organism the more transposable elements. Although we find more transposable elements in higher evolved organisms this rule can not be maintained if compared single species as frogs and humans.

Transposons most often code for transposase the enzyme responsible for the transposon dislocation. As Transposons are so common in a genome it is not surprising that transposases are the most common genes in a genome [2].

References

1. Christian Biémont und Cristina Vieira, „Genetics: junk DNA as an evolutionary force“, Nature 443, Nr. 7111 (Oktober 5, 2006): 521-524.

2. Ramy K Aziz, Mya Breitbart, und Robert A Edwards, „Transposases are the most abundant, most ubiquitous genes in nature“, Nucleic Acids Research 38, Nr. 13 (Juli 2010): 4207-4217.