About BRCA1
The BRCA1 gene (BReast CAncer gene 1) on chromosome 17q21 encodes a tumor suppressor protein involved in DNA repair. Mutations in BRCA1 significantly increase the risk of breast, ovarian, and other cancers. BRCA1 spans ~100 kb of genomic DNA with 24 coding exons.
NCBI Gene ID: 672 | RefSeq: NM_007294.4 | Genomic: NC_000017.11 (43044295-43125364)
BRCA1 Primer Design Challenges
- Large gene size: 100+ kb requires careful amplicon selection
- High GC content in some exons: Exons 11 and 16 have 65-70% GC, requiring adjusted parameters
- Known pathogenic SNPs: Over 3,000 variants cataloged in ClinVar; primers must avoid these positions
- Pseudo-genes: BRCA1 has known pseudogenes that can cause non-specific amplification
- Clinical sensitivity: Diagnostic primers require the highest validation standards
Recommended Primer Design Parameters for BRCA1
| Parameter | Standard Exons | GC-Rich Exons (11, 16) |
|---|---|---|
| Primer length | 20-22 nt | 22-25 nt |
| GC content | 45-55% | 50-60% |
| Tm | 58-62°C | 60-65°C |
| Amplicon size | 150-300 bp | 200-350 bp |
| Annealing temp | 58-60°C | 62-65°C |
| PCR additive | Standard | Add 5% DMSO or 1M betaine |
Key SNPs to Avoid in Primer Binding Sites
When designing BRCA1 primers, avoid these high-frequency SNPs in the 3' region:
- rs80357906 (c.5266dupC) — Common pathogenic duplication
- rs80357914 (c.68_69delAG, 185delAG, p.Glu23fs) — Founder's mutation in Ashkenazi Jewish population
- rs28897672 (c.181T>G, p.Cys61Gly) — Exon 5 variant
- c.3756_3759del (p.Ser1253Argfs) — Recurrent Exon 11 deletion (no canonical dbSNP rs; LOVD 3494)
Clinical Validation Required
All BRCA1 primers designed with VigyanLLM are for research use only. Clinical diagnostic applications require additional wet-lab validation, Sanger sequencing confirmation, and regulatory approval before patient use.
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