Question

You are attempting to clone the human insulin gene into E.Coli so that you can have access to unlimited human insulin for medical use. Insulin is produced in pacreas, but you have human skin cells to work with.

2.) You have constructed a DNA probe, using the amino acid sequence of insulin (a short piece of DNA carrying a label, such as radioactivity, which can hybridize with your target DNA) to find your target gene. Explain whether your probe is a. single stranded or double stranded and why? b. Which part of the gene (introns, exons, promoter, etc.) is this probe binding to?

Answer 1

a.

The probe is single stranded only, because if probe has to hybridize with the target DNA, it has to be in single stranded condition only.

b.

Introns are the DNA sequences which do not code for RNA. Introns are removed by splicing process during maturation of the final RNA product.

Exons are the coding sequences of DNA. They are joined after mRNA splicing.

Promoter is the region from which transcription is initiated.

Thus the probe binds to all regions of target DNA. Because only in mature mRNA Exons are removed but not in DNA.