The process of introducing DNA into bacterial cells by applying a brief electrical pulse is:
A. Heat shock
B. Microinjection
C. Electroporation
D. Biolistics
Answer: Option C
Solution (By JKSSB Mock Tests)
Electroporation uses an electric field to create temporary pores in the cell membrane, allowing DNA to enter. Heat shock is a chemical method using CaCl₂ and temperature shift, microinjection physically injects DNA into cells, biolistics is a gene gun for plant cells. Electroporation is efficient for many cell types.
Explanation:
Azolla is an aquatic fern that harbors the nitrogen-fixing cyanobacterium Anabaena azollae in its leaf cavities. It is extensively used as a biofertilizer in rice paddies, adding organic nitrogen. Rhizobium fixes nitrogen in legume roots, Azotobacter is free-living in soil, mycorrhiza is a fungal association enhancing phosphorus uptake. Azolla multiplies rapidly and improves soil fertility.
Explanation:
During fertilization, when a capacitated sperm penetrates the outer layer of cumulus cells (corona radiata) and makes contact with the glycoprotein layer called the zona pellucida of the secondary oocyte, it triggers the acrosome reaction. The acrosome (a cap-like vesicle over the sperm head) releases hydrolytic enzymes (like acrosin) that digest a path through the zona pellucida, allowing the sperm to reach and fuse with the oocyte's plasma membrane.
Explanation:
The pleural cavity between the visceral and parietal pleura contains a thin layer of pleural fluid, lubricating the surfaces to reduce friction during lung expansion and contraction. Synovial fluid is in joints, cerebrospinal fluid surrounds the CNS, lymph is in the lymphatic system. Pleural effusion is excess accumulation.
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