MCQ
The compound rifampicin is very:
- APotent inhibitor of bacterial RNA polymerases
- BPotent inhibitor of bacterial DNA polymerases
- CWeak inhibitor of bacterial RNA polymerases
- DWeak inhibitor of bacterial DNA polymerases
Explanation:
Rifampicin serves as the potent inhibitor of bacterial RNA synthesis by binding to the beta-subunit of bacterial RNA polymerases thereby preventing the promoter clearance step of transcription. The active site of the enzyme is present in the cleft of beta and beta prime subunit.
Transcription initiation includes binding of polymerase to the promoter, forming initiation complex, followed by transcription initiation within the complex. This, in turn, leads to a conformational change to convert the complex to the elongation form that allows movement of the transcription complex away from the promoter. It is called promoter clearance.
Rifampicin does not affect any enzyme of DNA synthesis, making option B and D incorrect. Since the toxin affects the subunit responsible for promoter clearance step which is fundamental for elongation phase of protein synthesis; it is a potent inhibitor.
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$I.$ Recent studies support competition as suggested in 'Gauses's Competitive Exclusion Principle'
$II.$ Gause's hypothesis says if two species compete for same resources then one will be eliminated by another species
$III.$ More recent studies point out that species facing competition might evolve mechanisms that promote co-existence rather than exclusion
$IV.$ Gause's competitive exclusion principle is effective when resources are in excess
$V.$ Unlimited resources give better opportunity for adaptation
Choose the correct combination of statements
| a. | Trophoblast | i. | Embedding of blastocyst in the endome trium. |
| b. | Cleavage | ii. | Group of cells that would differentiate as embryo. |
| c. | Inner cell mass | iii. | Outer layer of blastocyst attached to the endometrium. |
| d. | Implantation | iv. | Mitotic division of zygote. |