A-LevelBiologyThe mitotic cell cycle9700/23 · May/June 2018 · Q16 Marks

Fig. 1.1 is a photomicrograph of root tip meristem. Different stages of the cell cycle are visible. Some cells are in the same stage of the cell cycle and some are in the same stage of mitosis. [Figure 1.1]

(a)Cell D and cell E are in the same stage of the cell cycle. State the difference between the nucleus of cell D and cell E.[1]
(b)Name the stage of mitosis occurring in each of cells A, B and C. cell A cell B cell C[3]
(c)Cells F and G are newly formed cells. Cytokinesis has occurred with the formation of a cell plate. Describe the events that have occurred in the stage of mitosis immediately before cytokinesis.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

[1] (nucleus of cell) D has two nucleoli v E has one nucleolus ;
[3] A = (early / mid) prophase; R late
B = (mid/late) prophase ; R early
C = anaphase ;
[2] I name of stage
two from:
ref. to (daughter) chromosomes at poles ; A (sister) chromatids at poles R chromatids move to poles A two separate groups of (daughter) chromosomes A two nuclei form (enclosing chromosomes) I there are two nuclei
in context of at each pole
nuclear envelope reassembles (around chromosomes); A nuclear membranes reassemble nucleolus reappears / nucleoli reappear ;
(daughter) chromosomes, become diffuse / become long and thin / decondense / uncoil ; A become chromatin I disappears
spindle, disassembles / AW ;

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