Question

First step in Southern blot technique:
(a) Digestion of DNA by restriction enzyme
(b) Production of a group of genetically identical cells
(c) Denature of DNA on the gel for hybridization with a specific probe
(d) Denature of DNA from a nucleated cell as from the scene of the crime

Answer 1

Hint: Blot in molecular biology and genetics is a method of transferring protein, DNA, or RNA onto a career to detect a specific DNA sequence in a blood or tissue sample. It is mainly used for the detection of proteins and nucleic acids, widely used for diagnostic reasons.

Complete step by step answer:
Southern blotting combines the transfer of electrophoresis- separate DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization.

- The method is named after its inventor Edwin Mellor Southern.
- First step in Southern blot- is the isolation of DNA from nucleated cells as from the scene of the crime.
1) The desired DNA is Isolated from the whole DNA present inside the nucleus.
2) Incubate specimens with detergent to promote cell lysis.
3) Lysis free cellular protein from DNA.
4) Proteins are enzymatically degraded by incubation with proteinase.
5) Organic or non- inorganic extraction removes protein
6) DNA is purified from the solution by alcohol precipitation.
7) Visible DNA fibers are removed and suspended in buffers.
So, the correct answer is,” Denature of DNA from a nucleated cell as from the scene of the crime”.

Additional information:
- Second step - DNA is restricted with enzymes.
- Third step - separated by electrophoresis.
- Fourth step - denature DNA with Alkali. This causes double- stranded DNA to become single- stranded.
- Fifth step - transfer the DNA to nitrocellulose paper i.e blotting.
- Sixth step - add labeled probe for hybridization.
- Seventh Step - blot is incubated with a wash buffer containing NaCl and detergent to wash away access probes and reduce background.
- Eight Step - Autoradiography.

Note:
- Southern blotting used to identify specific DNA in DNA samples.
- It is also used for the diagnosis of HIV- 1 and infectious diseases.
- In DNA fingerprinting.
Used in the prognosis of cancer and in prenatal diagnosis of genetic diseases.