Molecular analysis of fragile X syndrome.
The gene responsible for fragile X syndrome, fragile X mental retardation-1 (FMR1), contains an unstable repeat sequence of (CGG)(n). Additionally, an upstream promoter region of the gene--a CpG island--is abnormally methylated in most affected individuals. Amplification of CGG repeats and abnormal methylation show a correlation with affected status. The first basic and alternate protocols in this unit outline the use of the polymerase chain reaction (PCR) to rapidly detect the size of the repeat amplification. The second basic protocol describes the assessment of fragile X syndrome by direct Southern blot hybridization of genomic DNA digested with a pair of restriction enzymes, one of which is methylation-sensitive. Extent of amplification and level of methylation can be simultaneously detected. A combination of the two techniques can be used to characterize the genotypes of individual members in identified fragile X families.
Nolin
Sarah L
SL
Institute for Basic Research in Developmental Disabilities, Staten Island, New York, USA.
Dobkin
Carl
C
Brown
W Ted
WT
D001483:Base Sequence; D015139:Blotting, Southern; D018899:CpG Islands; D019175:DNA Methylation; D017931:DNA Primers; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics; D005600:Fragile X Syndrome / Q000235:genetics*; D006801:Humans; D016133:Polymerase Chain Reaction
D017931:DNA Primers; D051860:Fragile X Messenger Ribonucleoprotein 1; C497683:FMR1 protein, human