Biology 9700 · AS & A Level · Transport mechanisms
Transport mechanisms — practice question
Agrobacterium tumefaciens is a bacterium that can enter plants through wounds and trigger a disorder called crown gall disease. It attaches to the cell surface and transfers a small circular DNA molecule, called a plasmid, into the cell. Some genes on the plasmid produce proteins that alter the plant cell and lead to a plant tumour, or gall.
(a)[4]
Describe the alterations that take place during tumour formation.
(b)[1]
Bacteria that enter the stem through a wound can move to the root of the plant and cause damage. Suggest how the bacteria are able to reach the root of the plant.
(c)[2]
Fig. 6.1 shows $A.\ tumefaciens$ on the surface of cells of a tobacco plant $plumbaginifolia$. The cells $X$ and $Y$ are newly formed cells. Determine the actual length of cell $X$ in micrometres. Show your working. The magnification of Fig. 6.1 is $\times 11500$.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Protein synthesis and DNA replication increase” …