- Email: [email protected]
Physical Mapping
Physical Mapping I Schildkraut, New England Biolabs, Beverly, MA, USA
© 2001 Elsevier Inc. All rights reserved.
This article is reproduced from the previous edition, volume 3, p 1467, © 2001, Elsevier Inc.
In contrast to conventional genetic mapping, physical mapping is the process of demonstrating that two fragments of DNA both contain sequence in common. The two fragments may match each other precisely for thousands or millions of nucleo tides or they may have in common a run of sequence of only a dozen or so nucleotides. Usually, the identity between the DNA fragments is revealed by hybridizing a labeled DNA fragment to a complex mixture of unlabeled DNA fragments which have been separated by gel electrophoresis and transferred by blot ting to a membrane. All of the DNA bands on the membrane which have become associated with the labeled fragment (probe) have sequence in common with the probe. Physical mapping can also refer to a method of identifying a DNA fragment that carries a particular function by changing the
Brenner’s Encyclopedia of Genetics, 2nd edition, Volume 5
size of the DNA fragment. Introduction of either a sizeable deletion or insertion into a gene carried on a plasmid will concomitantly alter the size of the restriction fragment of DNA which carries the gene. Therefore, analyzing the sizes of DNA restriction fragments from a plasmid which carries the gene of interest whose function has been altered by transposon insertion will reveal a DNA fragment whose size has been increased. This larger DNA fragment corresponds (maps) to the gene that has been altered.
See also: DNA Hybridization; Gene Mapping.
doi:10.1016/B978-0-12-374984-0.01162-1
327
© 2001 Elsevier Inc. All rights reserved.
This article is reproduced from the previous edition, volume 3, p 1467, © 2001, Elsevier Inc.
In contrast to conventional genetic mapping, physical mapping is the process of demonstrating that two fragments of DNA both contain sequence in common. The two fragments may match each other precisely for thousands or millions of nucleo tides or they may have in common a run of sequence of only a dozen or so nucleotides. Usually, the identity between the DNA fragments is revealed by hybridizing a labeled DNA fragment to a complex mixture of unlabeled DNA fragments which have been separated by gel electrophoresis and transferred by blot ting to a membrane. All of the DNA bands on the membrane which have become associated with the labeled fragment (probe) have sequence in common with the probe. Physical mapping can also refer to a method of identifying a DNA fragment that carries a particular function by changing the
Brenner’s Encyclopedia of Genetics, 2nd edition, Volume 5
size of the DNA fragment. Introduction of either a sizeable deletion or insertion into a gene carried on a plasmid will concomitantly alter the size of the restriction fragment of DNA which carries the gene. Therefore, analyzing the sizes of DNA restriction fragments from a plasmid which carries the gene of interest whose function has been altered by transposon insertion will reveal a DNA fragment whose size has been increased. This larger DNA fragment corresponds (maps) to the gene that has been altered.
See also: DNA Hybridization; Gene Mapping.
doi:10.1016/B978-0-12-374984-0.01162-1
327