Fig. 1 shows a microscope field from a growing root tip. A student prepared the slide from a plant used to test soil quality near a construction site. Some ...
Question 1 Report
Fig. 1 shows a microscope field from a growing root tip. A student prepared the slide from a plant used to test soil quality near a construction site. Some of the cells are at different stages of mitosis. Twelve cells can be seen and three show clearly visible chromosomes.
(a) Use Fig. 1 to calculate the percentage of cells that show visible chromosomes. [2]
(b) Name the type of cell division taking place and describe two features of a cell at metaphase. [3]
(c) Explain why a root tip was used rather than a mature leaf to observe the stages of cell division. [3]
(d) Draw a simple cell at anaphase. Include two groups of chromosomes moving towards opposite sides of the cell. [4]
Answer Details
(a) Three of the twelve cells show visible chromosomes.
\[\frac{3}{12}\times100=25\%\]
Therefore, 25% of the cells show visible chromosomes. [2]
(b) The division is mitosis. At metaphase, chromosomes line up at the equator, or centre, of the cell. Each chromosome consists of two chromatids; spindle fibres may also be attached to the chromosomes. [3]
(c) A root tip contains growing tissue making new cells, so many cells are dividing by mitosis. This gives a good chance of seeing different mitotic stages. Mature leaf cells are mostly specialised and divide much less frequently. [3]
(d) At anaphase, sister chromatids have separated and move towards opposite poles of the cell.
The cell outline, two separate chromosome groups, their movement towards opposite sides, and separated V-shaped chromatids gain the marking points. [4]
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