All cells arise from other cells：練習題

During the process of binary fission in prokaryotic cells, how is the replication and segregation of the genetic material managed to ensure daughter cells are viable?

During the cell cycle, a specific drug prevents the attachment of spindle fibres to the centromeres of chromosomes. In which stage of mitosis will the cell most likely be arrested, and what will be the arrangement of the chromosomes?

In the eukaryotic cell cycle, a specific drug inhibits the action of DNA polymerase. If this drug is added to a culture of actively dividing cells, which transition in the cell cycle will be most directly prevented?

During prophase of mitosis, the DNA has already been replicated. Which of the following correctly describes the state of the genetic material at this specific stage?

During binary fission in prokaryotes, which statement correctly describes the behavior of the genetic material?

A prokaryotic cell reproduces via binary fission. Contrast the replication and segregation of circular DNA with that of plasmids in the production of daughter cells.

During binary fission in a bacterium, the circular DNA and plasmids are replicated. Contrast the method of segregation for the circular DNA with that of the plasmids in ensuring the production of two viable daughter cells.

A student observed a micrograph of 200 plant cells and recorded the following counts: 170 in interphase, 15 in prophase, 8 in metaphase, 4 in anaphase, and 3 in telophase. Calculate the mitotic index for this tissue and explain how uncontrolled cell division can lead to the formation of a tumour.

The cell cycle is a highly regulated process that ensures the genetic continuity of eukaryotic cells.

a) A student observes a root tip squash and identifies a cell where the chromatids are being pulled toward opposite poles of the cell. Identify this stage of mitosis and describe the role of spindle fibres in this process. (2 points)
b) Contrast the process of mitosis with binary fission in terms of the replication and segregation of genetic material. (3 points)
c) Explain how uncontrolled cell division can result in the formation of a malignant tumour. (2 points)

Vincristine is a chemotherapy drug used to treat cancer. It works by preventing the formation of spindle fibers during mitosis.

a) Identify which stage of mitosis would be most directly affected by Vincristine and describe the appearance of the cell at this stage. (2 points)
b) Explain why preventing the formation of spindle fibers stops the cell cycle and the further growth of a tumor. (3 points)
c) In a root tip squash experiment, a student counted 20 cells in mitosis out of a total of 250 cells. Calculate the mitotic index for this tissue. (2 points)