= Plasmid feature map
A <plasmid feature map> records the positions of specified <DNA> features. Construct an original circular example of total length $L=6000$ <base pairs>. Coordinates run clockwise from a chosen zero, and $0$ and $6000$ label the same boundary. Positions here denote boundaries between <base pairs>, so the interval from 1000 to 2500 contains $2500-1000=1500$ <base pairs>. This convention avoids counting both endpoints as additional material.
\Image[/plasmid-circular-vector-feature-map.png]
{title=An original 6000-<base pair> <plasmid feature map>: copying, selection and a chosen <plasmid insert> occupy distinct regions}
{description=Hypothetical engineered circular <DNA>, with clockwise boundary coordinates. Blue marks an <origin of replication> at 200–700; green marks a <selectable marker> at 3200–4000; orange marks the <plasmid insert> at 1000–2500. Abstract <restriction enzymes> A and B cut at the labelled boundaries: A at 1000; B at 2500 and 4500. Their recognition <nucleotide sequences> are unspecified. Neither the feature intervals nor the total length describe a real commercial construct. The ring records position, not the physical shape or three-dimensional conformation of <DNA>.}
The <origin of replication> is assigned to 200–700, the <selectable marker> to 3200–4000 and the <plasmid insert> to 1000–2500. Other positions are unspecified <DNA>, not empty gaps. Their lengths account for the entire circle:
$$
500+800+1500+3200=6000.
$$
The first three terms are the marked regions; the last is all remaining material. Choosing a coordinate zero does not add a physical break. Rotating every coordinate by the same amount changes the drawing's labels without changing any distance around the <plasmid>.
A <gene promoter> must function in the recipient for the intended <gene expression>; copying a <plasmid> alone does not establish <gene expression>.<Molecular Biology Reference by Addgene>[Plasmid Elements, Promoter Region row: recipient-dependent transcriptional machinery]{ref} The map therefore supports three separate questions: can the carrier persist, can carriers be recovered, and can the selected <DNA> perform the proposed task? The <galactose induction> comparison illustrates the third question in an actual <yeast> experiment.
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