Many antibacterial agents and chemotherapy agents act as topoisomerase inhibitors. Why would inhibition of topoisomerase cause cell death in bacterial and eukaryotic cells?
What will be an ideal response?
During DNA replication, as DNA strands unwind it creates torsional stress that accumulates as the unwound region gets larger. Without free ends, covalently closed circular DNA readily accumulates superhelical twists (supercoiled DNA). The accumulating stress could break the DNA template at random locations, potentially leading to a breakdown of DNA replication and, ultimately, to cell death. Topoisomerases prevent this lethal event by catalyzing a controlled cleavage and rejoining of DNA, thus enabling over-twisted strands to unwind. Topoisomerase inhibitors block the ligation step of the cell cycle, generating single- and double-stranded breaks that harm the integrity of the genome and ultimately result in apoptosis of the cancer cells or bacteria.
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A) human sense of taste B) pain receptors in birds C) human sense of smell D) lateral line systems in fish E) eyes in arthropods
Microscopically, this fungus appears barrel shaped with thick walls, which best describes which type of conidia?
a. Macroconidia b. Chlamydoconidia c. Arthroconidia d. Blastoconidia
A DNA sequence can be patented if
A) two or more people isolate the same sequence successfully. B) it forms a single gene. C) it has economic implications. D) it is useful as a tool for research or as a novel or improved product.
The release of which of the following neurotransmitters is stimulated by all major addictive drugs?
a. dopamine b. GABA c. serotonin d. acetylcholine