Question

Explain how exonization of mobile DNA elements might contribute to the evolution of complex transcription units.

Answer 1

Ans. -

Transposons elements are DNA sequences that are capable of integrating into the genome at a new site within the cell of its origin. Sometimes, the change in their positions creates or reverses mutations, thereby altering the cell's genotype. There are at least two classes of TEs: Class I TEs or retrotransposons generally function via reverse transcription, while Class II TEs or DNA transposons encode the protein transposase, which they require for insertion and excision, and some of these TEs also encode other proteins.

Transposable elements are primarily responsible for the DNA losses and gains in genome sequences that occur over time within and between species. TE insertions can provide evolutionary novelty for the regulation of gene expression, their overall impact on the evolution of gene expression is unclear. Transposable Elements have been shown to alter gene regulation and drive genome evolution. TEs can exert these effects on genes by altering chromatin structure, providing novel promoters or insulators, novel splice sites or other post-transcriptional modifications to re-wire transcriptional networks important in development and reproduction.

Also known as “jumping genes”, transposable elements (TEs) are discrete pieces of DNA that can move from site to site within genomes. As the sequences of human and other primate genomes are analyzed in increasing detail, we are begining to understand the scale and complexity of the past and current contribution of non-LTR retrotransposons to genomic change in the human lineage.