AP BIOLOGY

Detailed explanation-1: -Explanation: The IS elements are the most common type of transposons present in the bacterial genome. An inverted repeat of usually 50 bp is the hallmark of such elements present at each end of an insertion sequence. Explanation: A set of two direct repeats flank the IS element on either side.

Detailed explanation-2: -Direct repeats can align out of register in duplex DNA, whereas inverted repeats can pair with themselves along the same DNA strand, forming hairpins and cruciforms. For these reasons, both direct and inverted repeats can form DNA conformations that differ from the usual duplex B-form.

Detailed explanation-3: -Background: An inverted repeat is a DNA sequence followed downstream by its reverse complement, potentially with a gap in the centre. Inverted repeats are found in both prokaryotic and eukaryotic genomes and they have been linked with countless possible functions.

Detailed explanation-4: -After the transposon is ligated to the host DNA, the gaps are filled in by Watson-Crick base pairing. This creates identical direct repeats at each end of the transposon.

Detailed explanation-5: -DNA transposons, also known as class 2 transposable elements, are flanked at both ends by terminal inverted repeats. The inverted repeats are complements of each other (the repeat at one end is a mirror image of, and composed of complementary nucleotides to, the repeat at the opposing end).