Q 9. A fragment of DNA is composed of 100 000 bp. Assume that restriction endonucleases recognize 4-8bp
sequences (Use 4). Calculate the expected frequency of cuts if the recognition site is 6 bp long and the number
of cuts.
Answers
Answer:
Set 5 Answers
1.a. The frequency of cutting in a random DNA sequence for a given restriction enzyme is once per every 4n, where n is the number of bases in the restriction enzymes recognition sequence. The “4” derives from the fact that there are four different possible nucleotides that may be inserted at any one position (G, A, T, or C).
Eco RI and Hin dIII have a six-base recognition site, so they will cut once per every 46, or 4096 bases.
Hin dII has a five-base recognition site, so it will cut once per every 45, or 1024 bases.
Hpa II has a four-base recognition site, so it will cut once per every 44, or 256 bases.
b. To determine the number of sites, divide the number of bases in the DNA by the average length of the restriction fragments resulting from the given enzyme. The size of l is 48,502 base pairs, so the number of expected sites are:
Site
Eco RI
Hin dIII
Hin dII
Hpa II
Expected (A+T=C+G)
12
12
48
>50