During heat shock treatment to the bacterium, the temperature used is:
A. 5°C
B. 100°C
C. -196°C
D. 42°C
Answer (1)
The process being asked about is heat shock treatment, which is commonly used in molecular biology, specifically in the transformation of bacteria.
During heat shock treatment, bacterial cells are exposed briefly to a high temperature to make them more permeable to DNA. This is part of the transformation process, where plasmid DNA is introduced into bacterial cells.
In this procedure, the correct temperature used for the heat shock step is typically 42°C.
Here's why and how it works:
Preparation: Bacterial cells are first made competent using a calcium chloride solution, which helps to stabilize the negatively charged DNA and phospholipids in the bacterial cell membrane.
Heat Shock: After the bacteria and plasmid mixture are incubated on ice, they are quickly exposed to 42°C for a short time (usually about 30-45 seconds). This sudden increase in temperature causes the formation of pores in the bacterial cell membrane.
Effectiveness: The high temperature destabilizes the cell membrane, allowing the plasmid DNA to enter the bacterial cells more easily.
Recovery: After the heat shock, the cells are placed back on ice and then allowed to recover at a moderate temperature, which helps the cell membrane to reseal and the bacteria to express the genes on the new plasmid DNA.
So, in response to the multiple-choice question, the correct answer is:
(D) 42°C
This procedure is a common technique used in laboratories that need to genetically modify bacteria for research, biotechnology, or industrial applications.
