Discussion
A transposon is best described as
Answer: B
Correct answer: a DNA sequence that can move to a new position within the genome
A transposon, or transposable element, is a DNA sequence able to change its position within the genome. They were discovered in maize by Barbara McClintock in the 1940s, work for which she received the Nobel Prize in 1983 - long after it was first dismissed. The simplest form is the insertion sequence, carrying only the transposase gene needed for its own movement, flanked by inverted repeats. A composite transposon has two insertion sequences flanking additional genes, which are carried along with it - and those genes are frequently antibiotic resistance determinants, which is how resistance moves between plasmids and chromosomes. Movement may be conservative, cutting the element out and pasting it elsewhere, or replicative, copying it so that both sites end up occupied. Insertion into a gene disrupts it, so transposons cause mutations, and that property is exploited deliberately in transposon mutagenesis to identify gene function.
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