Question

Enzymes: SstI, TaqI, PmeI

Questions:

1) What are the following recognition sites for the following three enzymes?

2) Which of the following enzymes would cut a random plasmid the fewest times. Please explain

Answer 1

1. SstI recognition sequence
...GAGCTC...
...CTCGAG...

The probability of the sequence is 1/4 * 1/4 * 1/4 * 1/4 * 1/4 * 1/4 = 1/4096.
For every 4096 nucleotide, the occrance chance is once.

2. TaqI recognition sequence
...TCGA...
...AGCT...

The probability of the sequence is 1/4 * 1/4 * 1/4 * 1/4 = 1/256.
For every 256 nucleotide, the occrance chance is once.

3. PmeI recognition sequence
...GTTTAAAC...
...CAAATTTG...

The probability of the sequence is 1/4 * 1/4 * 1/4 * 1/4 * 1/4 * 1/4 * 1/4 * 1/4 = 1/65536.
For every 65536 nucleotide, the occrance chance is once.

Out of three, the PmeI will restrict the plasmid at fewest times.