Answer
a) To identify the genes expressed in a specific cell type, use mRNA from that cell type. Fluorescently label the mRNAs and use them to probe a DNA microarray, which will show which genes are represented in the mRNAs.
b) To identify and isolate the gene, use the amino acid sequence and the genetic code to predict the DNA sequence of the gene. Then, design PCR primers to amplify the gene. These can be used to amplify the gene, which can then be cloned into a suitable bacterial plasmid vector.
c) Transform bacteria with this plasmid and grow up the bacteria. The plasmid DNA can be extracted, and the gene copies obtained by restriction enzyme digestion and gel electrophoresis to clean up the DNA.
d) The gene can be expressed in bacteria provided that the copy in the plasmid has a bacterial promoter and that introns have been removed, which will automatically be true if cloning starts first with mRNA from cells which express the neurotransmitter.
Work Step by Step
This question asks you to review the chapter and see the overall process of cloning a gene and studying its product. Skim the chapter and make a list of relevant techniques to help you assemble the answer. Pay special attention to the fact that the amino acid sequence of the protein is known, allowing the use of PCR, which is a relatively quick and efficient method.
