Nd Phase

dsDNA

Insertion into another site in host dna

DNA somewhere else in cell

Retrotransposon long, contains a gene encoding reverse transcriptase and is flanked by direct repeats of 334 bp that correspond to the long terminal repeats (LTRs) of a retrovirus (Fig. 5.16).

When moving, the first step is to make a single stranded RNA copy (Fig. 15.17). The host provides the RNA polymerase II that transcribes the Ty-1 element starting in the left hand LTR. Next, reverse transcriptase makes a double stranded DNA copy. First it makes a single strand of DNA, so creating an RNA/DNA hybrid. A second round of synthesis replaces the RNA with DNA, forming double-stranded DNA. Finally, the DNA is inserted into a new site within the host cell DNA. There are 30 to 40 copies of Ty1 per yeast cell.

long terminal repeats (LTRs) Direct repeats of several hundred base pairs found at the ends of retroviruses and some other retro-elements

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