Methods for detecting the presence of expanded CGG repeats in the FMR1 gene 5′ untranslated region

1. A method for performing PCR to determine the presence or absence of an allele with expanded CGG repeats of the 5′ untranslated region (“UTR”) of the fragile X mental retardation 1 (“FMR1”) gene in a biological sample from a subject, said method comprising amplifying the CGG repeat region of said 5′ UTR region of the gene with a first primer and a second primer, wherein

(a) said first primer is complementary to a portion of the 5′ UTR region that is outside of the CGG repeat region; and,

(b) said second primer is a chimeric primer comprising 3 to 30 consecutive repeats of CCG or 3 to 30 consecutive repeats of CGG at the 3′ end of the second primer and a random nucleotide sequence at the 5′ end of the second primer.

2. The method of claim 1 , wherein said first primer has the sequence of SEQ ID NO.:1.

3. The method of claim 1 , wherein the random nucleotide sequence is a sequence of 18-35 nucleotides.

4. The method of claim 3 , wherein the random nucleotide sequence is a sequence of 21-30 nucleotides.

5. The method of claim 1 , wherein said second primer consists of 4 to 8 repeats of CCG at the 3′ end and a random nucleotide sequence of 18-35 nucleotides at the 5′ end.

6. The method of claim 5 , wherein said second primer consists of 4 repeats of CCG at the 3′ end and a random nucleotide sequence of 18-35 nucleotides at the 5′ end.

7. The method of claim 1 , wherein said subject is a newborn.

8. The method of claim 7 , wherein said biological sample is a blood spot.

9. The method of claim 1 , wherein said subject is a female.

10. The method of claim 1 , wherein said subject is a male.

11. The method of claim 3 , wherein 30 to 70% of the nucleotides in the random nucleotide sequence are A or T nucleotides.