#1 A 3.1-kilobase linear fragment of DNA was digested with PstI andproduced a 2.

Question

#1

A 3.1-kilobase linear fragment of DNA was digested with PstI andproduced a 2.0-kb and a 1.1-kb fragment. When the same 3.1 –kb fragment was cut with Hind…, it yielded a 1.5 kb fragment,a 1.3-kb fragment, and a 0.3 fragment. When the 3.1 kb molecule wascut with a mixture of the two enzymes, fragments of 1.5, .08, 0.5,and 0.3 kb resulted. Draw a map of the original 3.1-kb fragment,and label the restriction sites and the distances between thesesites.

#2

A friend brings you three samples of nucleic acid and asks youto determine each sample’s chemical identity (whether DNA orRNA) and whether the molecules are double-stranded orsingle-stranded. You use powerful nuclease to degrade each samplecompletely to its constituent nucleotides and then determine theapproximate relative proportion of nucleotides. The results of yourassay follow. What can you tell your friend about the nature ofthese samples?

Sample1: dGMP 13%    dCMP14%        dAMP36%        dTMP 37%

Sample 2: dGMP 12%    dCMP 36%       dAMP47%        dTMP 5%

Sample 3: GMP 22%      CMP 47%          AMP17%          UMP14%

Explanation / Answer

1.5kb               0.8 kb    0.5 kb 0.3 kb ---------------!---------!--------!---- HindIII         PstI       HindIII Sample 1: dGMP & dCMP and dAMP &dTMP are similar, hence itis double-stranded DNA. (d stands for deoxy hence it is DNA notRNA) Sample 2: single-stranded DNA Sample 3: single stranded RNA, (although there may be some doublestranded A-U regions because the %-ages are close)

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