Question 40 Answer and Explanation _ACT April 2022 Form Z08 Science Section

Passage VI

Microtubules (MTs), which are structural components of cells, continuously elongate and shorten. An MT in catastrophe stops elongating and starts to shorten. An MT in rescue stops shortening and starts to elongate. When a cell enters mitosis from interphase, these transitions contribute to the rearrangement of the MT structure to form the mitotic spindle.

Table 1 shows the values of 3 parameters that were set in 6 computer-simulation models (CSMs A—F) of MT populations. It also shows the known values of the parameters for interphase cells and mitotic cells.

Figure 1 compares, for 3 MT characteristics, the average values predicted by the CSMs with the known average values for the 2 cell types.

Table and figure adapted from N. R. Gliksman et al. , "How the Transition Frequencies of Microtubule Dynamic Instability (Nucleation, Catastrophe, and Rescue) Regulate Microtubule Dynamics inInterphase and Mitosis: Analysis Using a Monte Carlo Computer Simulation." ©1993 by The American Society for Cell Biology.

40. Based on Table 1 and Figure 1, which of the following changes most likely does NOT occur when the MT structure rearranges to form the mitotic spindle ?

F. An increase in the number of MTs

G. A decrease in the average MT length

H. An increase in the average MT elongation velocity

J. An increase in the average MT half-life

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

From the last sentence of the first paragraph, we can see that the motitic spindle refers to a cell enters mitosis from interphase, so compare the values of interphase cells and mitotic cells in table 1 and figure 1.