You cloned a 2-kb fragment of DNA into a bacterial cloning vector and want to construct a restriction map of the insert.You amplify the 2-kb insert using PCR, purify it, and subject it to differential digestion with the enzymes EcoRI and HindIII, gel-fractionate the digests, and visualize the restriction patterns by staining the gels with ethidium bromide to generate the following results.Using these data, which two loci would be CLOSEST on a genetic map if the frequency of crossing over is equal in this region?
A)The EcoRI sites that are 100 bp apart would show the smallest distance in cM.
B)The HindIII sites that are 750 bp apart would show the smallest distance in cM.
C)The HindIII site and the EcoRI site that are 200 bp apart would show the smallest distances in cM.
D)The EcoRI site and the HindIII site that are 300 bp apart would show the smallest distance in cM.
E)The EcoRI sites that are 150 bp apart would show the smallest distance in cM.

Question

You cloned a 2-kb fragment of DNA into a bacterial cloning vector and want to construct a restriction map of the insert.You amplify the 2-kb insert using PCR, purify it, and subject it to differential digestion with the enzymes EcoRI and HindIII, gel-fractionate the digests, and visualize the restriction patterns by staining the gels with ethidium bromide to generate the following results.Using these data, which two loci would be CLOSEST on a genetic map if the frequency of crossing over is equal in this region? 
A)The EcoRI sites that are 100 bp apart would show the smallest distance in cM. 
B)The HindIII sites that are 750 bp apart would show the smallest distance in cM. 
C)The HindIII site and the EcoRI site that are 200 bp apart would show the smallest distances in cM. 
D)The EcoRI site and the HindIII site that are 300 bp apart would show the smallest distance in cM. 
E)The EcoRI sites that are 150 bp apart would show the smallest distance in cM.

Quizplus · Accepted Answer

The HindIII site and the EcoRI site that are 200 bp apart would show the smallest distances in cM because they are closest to each other on the physical map and are likely to have the lowest frequency of crossing over. The other options have larger distances between the restriction sites, and therefore, they are expected to have a higher frequency of crossing over.

You Cloned a 2-Kb Fragment of DNA into a Bacterial