Retrotransposons and retroposons: Subtle nuances

The transposable elements that transpose via an RNA intermediate are of two kinds: Retrotransposons and retroposons.
1) Retrotransposons: They resemble retroviruses and encode reverse transcriptase enzyme.
2) Retroposons: Neither do they resemble retroviruses nor do they code for their own reverse transcriptase.
Retrotransposons: The genetic information of retroviruses is encoded in RNA, which is transcribed into DNA by [...]

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The Ac-Ds Transposon System contd…

The transposase recognizes sequences at the inverted terminal repeats and excises the element at those sites. Ac produces functional transposase; Ds cannot produce the functional enzyme due to deletions. The inverted terminal repeats are the same in both Ac and Ds elements, and transposase recognizes them and transposes both Ac and Ds elements. If there [...]

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The Ac-Ds Transposon System contd…

Ds elements, unable to excise themselves, can be excised and moved to a new location if an Ac element is present somewhere in the genome. Thus an Ac (activator) element activates transposition of a Ds element. In the absence of an Ac element, a Ds element remains in the gene and the allele behaves [...]

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The Ac-Ds Transposon System

The Ac-Ds system of maize is a muatble allele system. It was on the basis of studies on this system that Barbara McClintock proposed the concept of transposable elements. She received the 1984 Nobel Prize in medicine for her pioneering work on transposons.
Transposons, by inserting themselves into genes, cause mutations, and disrupt the trasncription of [...]

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Transposable Elements: Dispersed Repeats

 Transposable elements fall under the category of dispersed sequence repeats. Transposable elements are the sections of DNA that move or transpose within the genome. They are also sometimes referred to as molecular parasites, as they exist only to maintain and propagate themselves and have no specific function in the biology of their host. However, some [...]

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