NEETZoologyBiotechnology and Its Applications
A patient is suspected of having a genetic mutation. During molecular diagnosis, a single-stranded DNA tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells, followed by detection using autoradiography. It is observed that the clone having the mutated gene does not appear on the photographic film. What is the biological reason for this observation?
Options
- AThe mutated gene actively degrades the radioactive probe before detection.
- BThe probe lacks complementarity with the mutated gene and fails to hybridise.
- CThe probe hybridises successfully but loses its radioactivity due to the mutation.
- DThe mutated gene is not transcribed into mRNA, preventing the probe from binding.
Correct answer
B. The probe lacks complementarity with the mutated gene and fails to hybridise.
Step-by-step solution
According to NCERT, a single-stranded DNA or RNA tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the mutated gene will not appear on the photographic film because the probe is designed to be complementary to the normal (wild-type) sequence. When a mutation alters the DNA sequence, the probe will not have complementarity with the mutated gene. Thus, it fails to hybridise, resulting in no radi