DNA Base Pair Calculator
Analyze a DNA sequence: count nucleotides, calculate GC content, generate the complementary strand, and estimate molecular weight. Enter the sequence using standard IUPAC nucleotide codes (A, T, G, C).
Sequence Analysis
Watson-Crick Base Pairing Rules
| Base | Name | Pairs With | Type |
|---|---|---|---|
| A | Adenine | T (2 H-bonds) | Purine |
| T | Thymine | A (2 H-bonds) | Pyrimidine |
| G | Guanine | C (3 H-bonds) | Purine |
| C | Cytosine | G (3 H-bonds) | Pyrimidine |
GC content (%) = (G + C) / total bases × 100. Higher GC content = higher melting temperature (Tm). Approximate Tm for short oligos: Tm ≈ 2(A+T) + 4(G+C) °C.
References & Methodology
- Watson, J.D. & Crick, F.H.C. (1953) — "Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid." Nature 171:737–738. Foundational base-pairing rules.
- Sambrook, J. & Russell, D.W. — Molecular Cloning: A Laboratory Manual (4th ed., CSHL Press) — Standard reference for DNA quantification, GC content analysis, and Tm calculations.
- IUPAC-IUB Commission on Biochemical Nomenclature — Standard one-letter nucleotide codes and molecular weight constants for DNA/RNA residues.