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Naturally Occurring Polymers—Animals
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
The third group is the LTR retrotransposons that are flanked by long, terminal, direct repeats that contain all the transcriptonal regulatory elements. LTR genes can encode a protease, reverse transcriptase, RNAse H, and integrase. Transposition occurs through a retroviral mechanism with reverse transcription occurring in a cytoplasmic virus-like particle. While a wide variety of LTRs exist, it is believed that only the endogenous retroviruses ( ERVs) are active in humans.
Inter-retrotransposon amplified polymorphism markers revealed long terminal repeat retrotransposon insertion polymorphism in flax cultivated on the experimental fields around Chernobyl
Published in Journal of Environmental Science and Health, Part A, 2020
Veronika Lancíková, Jana Žiarovská
Two major classes of TEs are known up to this date, I and II.[24] Class I of TEs represents retrotransposons, which transpose through reverse transcription of RNA and class II of TEs are DNA transposons which transposition do not involve RNA but cut-and-paste mechanism, and several transposase enzymes.[25] Retrotransposons are further divided into the LTR (Long Terminal Repeat) and non-LTR retrotransposon.[26] LTR-retrotransposons are classified into two major groups Copia and Gypsy consisting of many families which constitute from 40 to 70% of total genomic DNA.[27] Structural and functional characteristics of retrotransposons are similar to retroviruses but retrotransposons are not infectious in contrast to retroviruses.[28] Retrotransposons are largely quiescent during plant development and their activity in plant genomes is strictly controlled, although the transcription and transposition can be activated by different forms of abiotic and biotic stresses.[29,30] Retrotransposons as the most widespread class of TEs[31] are highly suitable for detection of genetic polymorphism. Molecular markers based on retrotransposon activity represent a pivotal techniques for analyses of genetic polymorphism and genomic changes in plants.[32] Various stress impulses, depending on stress factor and organism, may induce the specific response of LTR-retrotransposons activity. In photosynthetic eukaryotes, stress can activate the mechanism of retransposition termed „copy and paste”, thus reverse transcription and re-incorporation of retroelement into a new location in genome.[33] For instance, incorporation of activated LTR-retrotransposons within gene coding region may result in the inhibition of gene expression, furthermore the transcription activity of adjoining genes can be affected as well.[34,35]