Question

1. which of the following happens last during mitosis?

a. microtubules emerge from the centrosomes.
b. tetrads form.
c. the sister chromatids separate.
d. sister chromatids align on the metaphase plate.
e. the spindles start to pull on the kinetochores of sister chromatids.

Explanation:

To determine which event happens last in mitosis, we analyze each option:

• Option a: Microtubules emerging from centrosomes (spindle formation) occurs in prophase.
• Option b: Tetrads form during meiosis, not mitosis, so this is irrelevant.
• Option c: Sister chromatids separate during anaphase, which is later in mitosis but we need to check the last event.
• Option d: Sister chromatids align on the metaphase plate during metaphase, which is before anaphase.
• Option e: The spindles start to pull on kinetochores of sister chromatids occurs during anaphase, but the separation (option c) is the result of this pulling and happens after the initial pulling starts. Wait, no—actually, the sequence is: prophase (a), metaphase (d), anaphase starts with spindle pulling (e), and then sister chromatids separate (c). Wait, no, correction: In mitosis, the order of events related to chromosomes:

1. Prophase: Spindle forms (a), chromosomes condense.
2. Metaphase: Chromosomes (sister chromatids) align on metaphase plate (d).
3. Anaphase: Sister chromatids separate (c) as the spindle fibers pull them apart (the pulling starts and then separation occurs; but the separation is the key event of anaphase progression). Wait, actually, the process in anaphase is that the kinetochore microtubules shorten, pulling the sister chromatids apart (so the separation (c) is the result of the pulling (e), but the separation is the event that happens after the pulling starts. However, among the given options, let's re - evaluate:

• Tetrads (b) are for meiosis, so eliminate.
• Prophase: a (spindle formation).
• Metaphase: d (alignment).
• Anaphase: First, the spindle starts pulling (e), then sister chromatids separate (c). But the separation of sister chromatids (c) is a later event in anaphase than the start of pulling. Wait, no—actually, the pulling causes the separation. But in the context of the options, let's check the stages:

Mitosis stages in order: Prophase, Metaphase, Anaphase, Telophase.

• Prophase: Microtubules from centrosomes (a) form the spindle.
• Metaphase: Sister chromatids align (d) on metaphase plate.
• Anaphase: Sister chromatids separate (c) (this is the key event of anaphase, and the pulling (e) is part of the process that leads to separation. So the separation (c) happens after alignment (d) and the start of pulling (e). So among the options (excluding b which is meiosis - related), the last event is the separation of sister chromatids (c).

Answer:

c. The sister chromatids separate.