Aresearcher has sequenced a gene that has two alleles. she has a mixture of both alleles and clones them into e. coli using plasmids. she is interested in one particular allele that is correlated with a disease. how can she select those colonies that have the disease allele?

The blue-white screen refers to a procedure of screening that allows for the brisk and convenient determination of recombinant bacteria in vector-based molecular cloning experiments. In the process, the DNA of interest is ligated into a vector. The blue colonies constitute of self-relegated plasmids that are devoid of DNA inserts obstructing the lac Z gene.  

The white colonies contain bacteria that conduct plasmids, which possess the inserts of DNA fragments that obstruct the lac Z gene. Therefore, the researcher needs to sequence the plasmids of the white colonies prior to knowing which allele it constitutes.  

your answer is "the 1950's"