My teacher has given this question that nobody in the class seems to understand. Can anybody point me in the right direction?
Q. You wish to know whether the cDNA you have isolated and sequenced is the product of a
unique gene or is made by a gene that is a member of a family of related genes. To address
this questions, you digest cell DNA with a restriction nuclease that cleaves the genomic
DNA but not the cDNA, separate the fragments by gel electrophoresis, and visualize bands
using radioactive cDNA as a probe. The Southern blot shows two bands, one of which
hybridizes more strongly to the probe substance than the other.
You interpret the stronger hybridizing band as the gene that encodes your cDNA and the
weaker band as a related gene. When you explain your result to your advisor, she cautions
that you have not proven that there are two genes. She suggests that you repeat the Southern
blot in duplicate, probing one with a radioactive segment from the 5'-end of the cDNA and
the other with a radioactive segment from the 3'-end of the cDNA
A) How might you get two hybridizing bands if the cDNA was the product of a unique
gene?
B) What results would you expect from the experiment your advisor proposed if there were
a single unique gene? Or if there were two related genes?
Thanks in advance to any geniuses that can lend me a hand.