Question

Why was cdna and not genomic dna used in the commercial cloning of the human insulin gene in bacteria?

Answer 1

in the commercial cloning of the human insulin gene?Answer: The commercial cloning of insulin was into bacteria. Bacteria are not capable of processing introns. Genomic DNA would include the introns, while cDNA is a copy of processed (and thus intron-free) mRNA.21.After DrosophilaDNA has been treated with a restriction enzyme, the fragments are inserted into plasmids and selected as clones in E. coli. With the use of this “shotgun” technique, every DNA sequence of Drosophilain a library can be recovered. a. How would you identify a clone that contains DNA encoding the protein actin, whose amino acid sequence is known? b. How would you identify a clone encoding a specific tRNA? Answer: a.Because the actin protein sequence is known, a probe could be synthesized by “guessing” the DNA sequence based on the amino acid sequence. (This works best if there is a region of amino acids that can be coded with minimal redundancy.) Alternatively, the gene for actin cloned in another species can be used as a probe to find the homologous gene in Drosophila. If an expression vector was used, it might also be possible to detect a clone coding for actin by screening with actin antibodies. b.Hybridization using the specific tRNA as a probe could identify a clone coding for itself. 22.In any particular transformed eukaryotic cell (say, of Saccharomyces cerevisiae), how could you tell if the transforming DNA (carried on a circular bacterial vector) a. replaced the resident gene of the recipient by double crossing over or single crossing over? b. was inserted ectopically? Answer: a.The transformed phenotype would map to the same locus. If gene replacement occurred by a double crossing-over event, the transformed cells would not contain vector DNA. If a single crossing-over took place, the entire vector would now be part of the linear Saccharomyces chromosome.