102
FENG QIAN AND GREGORY G. GERMINO
Partial digestion, by virtue of increasing the number of bands detected in
each lane, complicates the process. The probability of a chance co-migration
occurring for two probes increases with the number of bands compared.
Thus the pattern of partial digestion must be similar for two probes before
they can be said to be physically linked. One other factor which affects the
probability of co-migration is the resolution of the gel from which the blot
was made.
The zone of Virtually all pulsed field gels have a zone near their top where there appears
limiting mobility tobe a "cloud" of very high molecular weight DNA. This region is called the
zone oflimiting mobility because DNA fragments in this portion of the gel
no Iongermigrate in a linearfashionproportional to their length. Fragments
differing by millions ofbase pairs in length migrate at the same rate ( and are
indistinguishable) in "the zone". The size of molecules trapped in the zone
depends on the pulse interval.
Specific protocols for DNA fragment resolution by pulsed field gel electrophoresis are provided in the next section.
References
Ausubel FM, Brent R, Kingston RE, Moore DD, Seidman JG, Smith JA, and Struhl K ( eds)
(1987) Current Protocols in Molecular Biology. Wiley Interscience
Carle GF, Frank M, and Olson MV (1986) Electrophoretic separation oflarge DNA molecules by periodic inversion of the electric field. Science 232:65- 68
Chu G, Vollrath D, and Davis RW ( 1986) Separation oflarge DNA molecules by contourclamped homogeneaus electric field. Science 234: 1582-1585
Clark SM, LaiE, Birren BW, and Hood L (1988) A novel instrument for separating large
DNA molecules with pulsed homogeneaus electric fields. Science 241:1203-1205
Schwartz DC and Cantor CR (1984) Separation of yeast chromosome-sized DNAs by
pulsed field gradient gel electrophoresis. Cell 37: 67- 75
FENG QIAN AND GREGORY G. GERMINO
Partial digestion, by virtue of increasing the number of bands detected in
each lane, complicates the process. The probability of a chance co-migration
occurring for two probes increases with the number of bands compared.
Thus the pattern of partial digestion must be similar for two probes before
they can be said to be physically linked. One other factor which affects the
probability of co-migration is the resolution of the gel from which the blot
was made.
The zone of Virtually all pulsed field gels have a zone near their top where there appears
limiting mobility tobe a "cloud" of very high molecular weight DNA. This region is called the
zone oflimiting mobility because DNA fragments in this portion of the gel
no Iongermigrate in a linearfashionproportional to their length. Fragments
differing by millions ofbase pairs in length migrate at the same rate ( and are
indistinguishable) in "the zone". The size of molecules trapped in the zone
depends on the pulse interval.
Specific protocols for DNA fragment resolution by pulsed field gel electrophoresis are provided in the next section.
References
Ausubel FM, Brent R, Kingston RE, Moore DD, Seidman JG, Smith JA, and Struhl K ( eds)
(1987) Current Protocols in Molecular Biology. Wiley Interscience
Carle GF, Frank M, and Olson MV (1986) Electrophoretic separation oflarge DNA molecules by periodic inversion of the electric field. Science 232:65- 68
Chu G, Vollrath D, and Davis RW ( 1986) Separation oflarge DNA molecules by contourclamped homogeneaus electric field. Science 234: 1582-1585
Clark SM, LaiE, Birren BW, and Hood L (1988) A novel instrument for separating large
DNA molecules with pulsed homogeneaus electric fields. Science 241:1203-1205
Schwartz DC and Cantor CR (1984) Separation of yeast chromosome-sized DNAs by
pulsed field gradient gel electrophoresis. Cell 37: 67- 75