What is the Difference Between Class I and Class II Transposable Elements?

Transposable elements are DNA sequences that can change their position within the genome, sometimes creating or reversing mutations and altering the genetic identity and genome size of the cell. They can be classified into two main classes based on their transposition mechanisms: Class I and Class II transposable elements.

Class I Transposable Elements (Retrotransposons):

• Use an RNA intermediate that is reverse-transcribed into a cDNA copy, which then reintegrates into a new genomic location.
• Their life cycle and structure are very similar to retroviruses.
• Retrotransposons begin as DNA and are transcribed into RNA via the normal mechanism. Reverse transcriptase and an endonuclease, which are generally coded for within their transposable element, are used to reverse transcribe the RNA back into DNA.

Class II Transposable Elements (DNA Transposons):

• Mobilized by a DNA intermediate or by replication involving a circular DNA intermediate.
• DNA transposons are characterized by the presence of terminal inverted repeats on both ends.
• They are not replicated like Class I elements but often include a transposase gene. Transposase is an enzyme that facilitates transposon movement.

In summary, the key difference between Class I and Class II transposable elements lies in their transposition mechanisms. Class I elements use RNA intermediates, while Class II elements use DNA intermediates.

Comparative Table: Class I vs Class II Transposable Elements

Class I and Class II transposable elements are mobile genetic elements or jumping genes that can change their position within the genome. They are categorized based on their transposition mechanism:

Class I Transposable Elements:

• Also known as retrotransposons.
• Transpose through an RNA intermediate.
• Require an RNA intermediate to integrate/duplicate themselves within a genome.
• Examples include non-LTR retrotransposons and LTR retrotransposons.

Class II Transposable Elements:

• Also known as DNA transposons.
• Transpose through a DNA intermediate.
• Do not use RNA as a transposition intermediate.
• Examples include bacterial insertion sequences and longer transposons.

Here is a table summarizing the differences between Class I and Class II transposable elements: