Ordering and Interpreting DNA Tests Pamela S. Karnes, M.D.  Mayo Clinic Proceedings  Volume 71, Issue 12, Pages 1192-1195 (December 1996) DOI: 10.4065/71.12.1192 Copyright © 1996 Mayo Foundation for Medical Education and Research Terms and Conditions

Fig. 1 Southern blot analysis. Lanes 1 through 5 contain DNA from five family members. In this two-fragment system, “A” refers to fragment size A and “B” refers to fragment size B. Each family member has two fragments, one from one member of a chromosome pair and one from the other member of the chromosome pair. When only one fragment seems to be evident, this reflects the fact that the fragments from both members of the chromosome pair are the same and are “on top of each other” on the gel. Mayo Clinic Proceedings 1996 71, 1192-1195DOI: (10.4065/71.12.1192) Copyright © 1996 Mayo Foundation for Medical Education and Research Terms and Conditions