Question

Taxol is a drug used in chemotherapy that interrupts the function of the mitotic spindle and prevents chromosomes from aligning properly. A cell treated with Taxol would:

A) arrest at the G1 checkpoint B) arrest at the S phase checkpoint C) arrest at the G2 checkpoint D) arrest at the M phase checkpoint E) go into the ‘resting’ G0 phase

Which of the following would you predict to find in an individual after 15 years of persistent opioid use? A) Increased gene expression of the gene encoding the dopamine re-uptake receptor protein, leading to higher amounts of dopamine in the synapse B) Reduced gene expression of the gene encoding the dopamine re-uptake receptor protein, leading to fewer dopamine re-uptake receptors in pre-synaptic neurons C) Increased gene expression of the gene encoding the dopamine receptor protein, leading to higher dopamine receptor levels in post-synaptic neurons D) Decreased gene expression of the gene encoding the dopamine receptor protein, leading to fewer dopamine receptor levels in post-synaptic neurons E) Reduced gene expression of the gene encoding dopamine

Answer 1

The cell treated with taxol would arrest at the M phase check point (Option D).

Taxol is used as drug in chemotherapy for the treatment of many type of cancer. The cancer cells have property of rapid cell division and taxol interferes with cell division. Taxol targets tubulin proteins which are involved in mitotic spindle apparatus formation. Mitotic spindle are required for proper chromosomal segregation because chromosomes are attached to spindle microtubules. Taxol acts by stabilizing microtubules polymer and thus inhibits the their disassembly. As a result, cells are not able to attain metaphase (one phase in M phase of cell cycle) spindle assembly and finally arrested in M phase (Mitotic phase). Prolong arrest in M phase triggers apoptosis/ cell death. Other Options A, B, C and E are not right because chromosome are visibly seen in M phase and they are arranged at the equator of cell with the help of spindle apparatus for proper segregation into daughter cells.