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

Structure of nucleic acids and replication of DNA — practice question

Cells within a tissue are often at different points in the cell cycle. Fig. 1.1 depicts cells at various stages of the cell cycle.
(a(i))[2]

Identify the stages of mitosis taking place in the cells labelled B and C in Fig. 1.1.

(a(ii))[3]

Describe how the chromosomes behave in the mitosis stage shown in cell A in Fig. 1.1.

(a(iii))[3]

Cell D in Fig. 1.1 is in interphase. Describe the function of DNA ligase in interphase.

(b(i))[1]

State the position of telomeres on a chromosome.

(b(ii))[2]

Some people with a long lifespan have cells showing higher than normal telomerase activity. Suggest why a long lifespan could be the result of higher telomerase activity.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: Stage B is identified as prophase (early/mid/late accepted)

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