DNA Sample #1 5’– T C C A G T G A T C T C G A A T T C G C T A G T A A C G T T C

Question

DNA Sample #1

5’– T C C A G T G A T C T C G A A T T C G C T A G T A A C G T T C G A T

3’– A G G T C A C T A G A G C T T A A G C G A T C A T T G C A A G C T A

DNA Sample #2

5’– T C A T C G A A T T C C T G G A A T C A G C A G A A T T C G C A T A

3’– A G T A G C T T A A G G A C C T T A G T C G T C T T A A G C G T A T

If both samples are treated with the restriction enzyme EcoRI [recognition sequence G’AATTC] then indicate the number of fragments and the size of each fragment from each sample of DNA. List the fragment sizes in order of largest to smallest.

Sample # 1                                                               Sample # 2

# of fragments:________                                      # of fragments:________

Sizes of fragments (large to small):                     Sizes of fragments (large to small):

Explanation / Answer

No. of fragements in sample 1 will be 2 as it is having only one recognition sequence i.e. GAATTC. Hence restriction enzyme will cut at this single recognition site consequently two fragements of DNA will produce. Sizes of fragements will be of 19 base pairs and 15 base pairs.

No. of fragements in sample 2 will be 3 as it is having two recognition sites i.e. GAATTC. Hence restriction enzyme will cut at two sites consequently 3 fragements will produce. Sizes of fragements will be of 18 base pairs (one fragement) and 8 base pairs (2 fragements).

Note: Here blunt cut is considered in which half of the base pairs of recognition sequence i.e. 3 base pairs (GAA) out of 6 base pairs (GAATTC) is moved with a fragement and other half base pairs of recognition sequence i.e. (TTC) goes with another fragements.

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