Biology 9700 · AS & A Level · Structure of transport tissues

Structure of transport tissues — practice question

Every meristem cell in a leaf bud can enlarge and divide by mitosis to form two daughter cells that are genetically identical to one another and to the cell that divided originally. Fig. 5.1 shows the stages in the mitotic cell cycle of a meristem cell.
(a(i))[4]

Outline and explain the events in S phase, metaphase and anaphase of the mitotic cell cycle that are crucial for producing genetically identical daughter cells.

(a(ii))[1]

Although they are genetically identical, daughter cells are not identical straight after cytokinesis. Suggest a reason why the daughter cells are not identical immediately after cytokinesis.

(b(i))[4]

In the young leaf, some cells produced by mitotic division become elongated cells that differentiate into xylem vessel elements. These xylem vessel elements join end to end to make xylem vessels. Suggest the structural changes that occur as elongated cells develop into xylem vessel elements and explain how these changes allow xylem vessels to carry out their transport function.

(b(ii))[1]

Fig. 5.2 shows a plan diagram of a transverse section through a dicotyledonous leaf. Add a label line and the letter X to Fig. 5.2 to show where the xylem tissue is located.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Replication of DNA in S phase produces identical DNA molecules

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