AP BIOLOGY

Detailed explanation-1: -Explanation: LTR-retrotransposons are also known as viral retrotransposons. They are most abundantly found in lower eukaryotes such as yeast and Drosophila.

Detailed explanation-2: -They are widespread in plants and fungi, probably retaining protein domains during evolution of these two kingdoms. It is thought that the chromodomain directs retrotransposon integration to specific target sites.

Detailed explanation-3: -Retrotransposons can be subdivided into two groups, distinguished by the presence or absence of long terminal repeats (LTRs). Human LTR elements are endogenous retroviruses which account for  8% of the genome (FIG. 1a).

Detailed explanation-4: -Common cut-and-paste transposons found in mammals include the Tc1/mariner, hATs, and piggyBac families, all of which can be characterized by their terminal inverted repeats–ranging in size from 10 to1, 000 bp–and the catalytic domains of their transposase (Fig.

Detailed explanation-5: -Distribution of Retrotransposons. Retrotransposons have only been found in eukaryotic genomes (with the exception of a few rare elements integrated into the genomes of eukaryotic viruses).