Diagram illustrating results of fragile X analysis by Southern blot
'N' denotes normal bands.

Examples given are:

Male, normal: A single band of normal size, unmethylated

Female, normal: Two bands of normal size, one unmethylated (on the active X chromosome) and one methylated (on the inactive X chromosome).

Male, premutation: A single band of increased size, unmethylated. This premutation has 75 repeats (sized by PCR analysis).

Female, premutation: A four-band pattern with an unmethylated (on the active X) and a methylated (on the inactive X) form of both the premutation and normal bands. This premutation has 92 repeats (sized by PCR analysis).

Male, full mutation: Band(s) with >200 repeats, methylated. Absence of a normal unmethylated band. In this case there are three different full mutation sizes, 280, 430 and 920 repeats (sized by Southern blot analysis).

Female, full mutation: Band(s) with >200 repeats, methylated. The two normal bands from the normal allele are also present. This full mutation has 355 repeats (sized by Southern blot analysis).

Male, mosaic: Full mutation and premutation. In this case the full mutation has 510 repeats (sized by Southern blot analysis) and the premutation has 84 repeats (sized by PCR analysis).

Annette K. Taylor, M.S., Ph.D.
Kimball Genetics, Inc.
101 University Boulevard, Suite 330
Denver, CO 80206
800-320-1807

© copyright 1998-2008 NFXF
This page last updated Tuesday, June 24, 2008