Problem Set


1.The enzyme ApoI has a restriction site: R^AATTY where R and Y are degenerate
nucleotideides. See the IUPAC table to identify the nucleotide possibilities
for the R and Y.

    Write a regular expression that will match occurrences of the site in a sequence. (hint: what are you going to do about the actual cut site, represented by the '^'?)

2. Use the regular expression you just wrote to find all the restriction sites in the following sequence. Be sure to think about how to handle the newlines!

GAATTCAAGTTCTTGTGCGCACACAAATCCAATAAAAACTATTGTGCACACAGACGCGAC
TTCGCGGTCTCGCTTGTTCTTGTTGTATTCGTATTTTCATTTCTCGTTCTGTTTCTACTT
AACAATGTGGTGATAATATAAAAAATAAAGCAATTCAAAAGTGTATGACTTAATTAATGA
GCGATTTTTTTTTTGAAATCAAATTTTTGGAACATTTTTTTTAAATTCAAATTTTGGCGA
AAATTCAATATCGGTTCTACTATCCATAATATAATTCATCAGGAATACATCTTCAAAGGC
AAACGGTGACAACAAAATTCAGGCAATTCAGGCAAATACCGAATGACCAGCTTGGTTATC
AATTCTAGAATTTGTTTTTTGGTTTTTATTTATCATTGTAAATAAGACAAACATTTGTTC
CTAGTAAAGAATGTAACACCAGAAGTCACGTAAAATGGTGTCCCCATTGTTTAAACGGTT
GTTGGGACCAATGGAGTTCGTGGTAACAGTACATCTTTCCCCTTGAATTTGCCATTCAAA
ATTTGCGGTGGAATACCTAACAAATCCAGTGAATTTAAGAATTGCGATGGGTAATTGACA
TGAATTCCAAGGTCAAATGCTAAGAGATAGTTTAATTTATGTTTGAGACAATCAATTCCC
CAATTTTTCTAAGACTTCAATCAATCTCTTAGAATCCGCCTCTGGAGGTGCACTCAGCCG
CACGTCGGGCTCACCAAATATGTTGGGGTTGTCGGTGAACTCGAATAGAAATTATTGTCG
CCTCCATCTTCATGGCCGTGAAATCGGCTCGCTGACGGGCTTCTCGCGCTGGATTTTTTC
ACTATTTTTGAATACATCATTAACGCAATATATATATATATATATTTAT



3. Determine the site(s) of the cut in the above sequence. Print out the sequence with "^" at the cut site.

    Hints:
        Use subpatterns (parentheses and $1, $2) to find the cut site within the pattern.
        Use s///

    Example: if the pattern is GACGT^CT the following sequence

    AAAAAAAAGACGTCTTTTTTTAAAAAAAAGACGTCTTTTTTT

    would be cut like this:

    AAAAAAAAGACGT^CTTTTTTTAAAAAAAAGACGT^CTTTTTTT



4. Now that you've done your restriction digest, determine the lengths of your fragments and sort them by length (in the same order they would separate on an electrophoresis gel).

    Hint: take a look at the split man page or think about storing your matches in an array. With one of these two approaches you should be able to convert this string:

       AAAAAAAAGACGT^CTTTTTTTAAAAAAAAGACGT^CTTTTTTT


    into this array:

    ("AAAAAAAAGACGT","CTTTTTTTAAAAAAAAGACGT","CTTTTTTT")