G Segment dsDNA Phages, Lysogens, Repetitious Segments

G Segment dsDNA Phages

	G Segment dsDNA Phages - When the Mu DNA extracted from mature particles is denatured and renatured, a G bubble is observed is some molecules. The bubble is attributed to the presence of the G segment in opposite, directions with reference to α and β. Paring of the G strand cannot take place when Mu strands carrying the G in opposite directions undergoes renaturation.
This is seen as a noncomplementary inversion loop. At either end of the G segment are inverted repititious sequences (gl and gl') about 50 base pairs long. Within the middle 1kb of G is another pair of inverted repetitious segments (g3 and g3'), which, along with g4, form an internal stem loop structure. gHg4+g3' is about 1kb long, and constitutes one-third of the entire G sequence g2 and g5 are each about I kb long.
The gene for G inversion function (gin) is located in the β region, close to or within G. The gin mutant is unable to invert the G segment: Mu particles grown by infection primarily contain the same G orientation. Inversion is seen mainly in Mu particles grown by induction of the Mu lysogens.