Transposon vs Retrotransposon
Transposons and retrotransposons are genetic components of DNA, and there are major differences between them. The percentage presence of these genetic materials varies across species, and their functions determine the fates of the organism with mutations and other phenotypically important changes. Transposons and retrotransposons are genes or collections of certain genes located in the DNA strands, and alterations of their locations have been the main causes for these consequences. However, this article intends to discuss the functions of these genes briefly and presents a comparison between transposons and retrotransposons.
What is Transposon?
Transposons are interesting fragments or segments of DNA with the ability to change the location of the DNA strand in the form of cut and paste mechanism. Because of this mobile nature of the transposons, these are known as jumping genes. Transposons are of two major types known as Class I Transposons and Class II Transposons. Usually, the Class II type is referred as the transposons and the Class I type is referred as the retrotransposons. The processes of cutting and pasting of mobile DNA segments are regulated by the enzyme transposase. The enzyme binds to the both ends of the transposon and cuts the phosphodiester bonds of the DNA strand, isolate the transposon, move it to the target site, and bind in the new location. However, this process is interesting to understand, as some transposons can only move to certain locations only because of the incompatibility of base sequences with the target site. Genes with one end of a single strand has the same base sequence with the other end of the other single strand are transposons with sticky edges, because those can bind to the sites of the target DNA strand with the same base sequence as in the sticky ends. However, this mobility of genes can cause changes of the genotype as well as in the phenotype of the organism. Scientists invented about the transposons and genetically modified food and organisms according to the preferred customisations were then made available. Highly productive agricultural crops, antibiotics with medicinal properties, livestock animals were some of the advantageously developed products after the invention of transposons by Barbara McClintock in 1940s.
What is Retrotransposon?
Retrotransposons are the Class I transposons, and these move through the genome through the mechanism of copy and paste. The mechanism of the mobility of retrotransposons involves few major steps such as copying of the gene segment of the DNA strand into RNA, transfer of the copy of RNA to the target site, transcription of the RNA sequence back to DNA using reverse transcriptase, and insertion of the gene into the new location of DNA strand of genome. The two ends of these retrotransposons usually have long terminal repeats with about 1000 base pairs, and those are used as identification features of these genes. These genes are easily amplified inside the genome, and the percentage of the retrotransposons in the human genome is about 50%. These could be quite dangerous as the causative virus of AIDS, HIV, and T-cell leukaemia virus have the retrotransposons in their RNA genomes. In fact, these viruses can bind the retrotransposons into any site of the human DNA strands with the use of reverse transcriptase and integrase. The integrase enzyme functions the same way as transposase in Class II transposons.
What is the difference between Transposon and Retrotransposon?
• Transposons are Class II jumping genes while retrotransposons fall in the category of Class I.
• Transposons function with the transposase enzyme whereas retrotransposons function with the use of two main enzymes known as reverse transcriptase and integrase.
• The terminal ends are much longer in retrotransposons than in transposons.
• Transposons are cut from the origin and pasted at the target; conversely, retrotransposons being copied from the origin into RNA and transcribed at the target.
• The moving of retrotransposons involves RNA but not in transposons.