Biology 9700 · AS & A Level · Structure of nucleic acids and replication of DNA

Structure of nucleic acids and replication of DNA — practice question

The ideal point in a mitotic cell cycle for getting a sharp view of chromosomes is the metaphase stage. Fig. 6.1 shows a scanning electron micrograph of a set of human chromosomes at metaphase.
(a)[2]

The cluster of chromosomes in Fig. 6.1 has been enlarged many times. The true width of the human chromosome between A-B is $1400\ \text{nm}$. Calculate the magnification of the scanning electron micrograph in Fig. 6.1.

(b)[4]

In the space provided, draw chromosome C from Fig. 6.1. Add labels to your drawing so that the chromosome's structure is shown.

(c)[1]

Suggest why the metaphase stage is the most suitable point in a mitotic cell cycle for getting a clear chromosome image.

(d)[1]

Name the stage of mitosis that comes immediately after metaphase.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: Correct calculation by dividing by $1400$

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