Certain unicellular eukaryotes, including diatoms and some yeasts, have mechanisms of nuclear division that may resemble intermediate steps in the evolution of mitosis. Which of the following is a characteristic feature of nuclear division in these organisms?
A) They reproduce by binary fission in their early stages of development and by mitosis when they are mature.
B) They have circular chromosomes that are segregated by a mitotic spindle.
C) Chromosomes are segregated by a mitotic spindle, but the nuclear envelope remains intact during division.
D) Chromosomes are segregated by attachment to the plasma membrane.

Question

Quizplus · Accepted Answer

Certain unicellular eukaryotes, including diatoms and some yeasts, have mechanisms of nuclear division that resemble intermediate steps in the evolution of mitosis. In these organisms, chromosomes are segregated by a mitotic spindle, but the nuclear envelope remains intact during division. This is because they lack the microtubule organizing centers required to form a complete spindle apparatus that can break down the nuclear envelope.

Certain Unicellular Eukaryotes, Including Diatoms and Some Yeasts, Have Mechanisms