Enzymes & vectors formulas
Restriction enzymes, cloning vectors and expression vectors. 2 formulas for GATE BT Recombinant DNA Technology and Tools, each with when to use it. Each is explained in the topic notes.
IAE Academy: Restriction enzymes, cloning vectors and expression vectors formulas (GATE BT)
All 2 Enzymes & vectors formulas
EXPECTED NUMBER OF SITES FOR A PALINDROMIC N-BP SITE IN RANDOM DNA
L is the length in bp, and all four bases have probability 1/4, independently. The expected average spacing between sites is 4^n bp: 256 bp for a 4-cutter, 4096 bp for a 6-cutter, 65,536 bp for an 8-cutter such as NotI (GC^GGCCGC). A palindromic site reads the same on both strands, so each position is counted once. A non-palindromic site can occur on either strand of dsDNA, which doubles the expected count. Real genomes differ from these values because base composition is biased and sequence is not random.
SITE PROBABILITY WHEN GC CONTENT IS NOT 50%
g is the GC fraction, so each of G and C has probability g/2 and each of A and T has probability (1−g)/2. n_GC and n_AT count the G/C and A/T bases in the site. The expected average spacing is 1/P_site bp (palindromic site).
Where this was asked: 2020 (4), 2022 (3), 2023 (2), 2024 (1). See the 10 previous-year questions on Enzymes & vectors. This shows what was asked, not what will be asked.