Objective 2 – The relationship between cell division and cell patterning Cell pa
ID: 144910 • Letter: O
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Objective 2 – The relationship between cell division and cell patterning
Cell patterning in roots exhibits a radial symmetry, which is established in the meristem byformative cell divisions. In the Arabidopsis SCARECROW (scr) mutant this symmetry is lost, indicating that the SCR gene functions to regulate formative division(s). Transverse sections of roots from either wild type or the scr mutant are shown in Figure 2.
Figure 2. Transverse sections of roots from wild-type (WT) or the scr (SCR) mutant of Arabidopsis thalianashowing tissue organization. The diagram at left illustrates the radial patterning of tissue organization in roots, and indicates each tissue layer that comprises the root in Arabidopsis thaliana.
(i) Based on your observations of Figure 2, what cell layer(s) in the scr mutant is missing?
(ii) Outline your reasons for reaching this conclusion.
SCr EpidermisWT Cortex Endodermis Pericycle Casparian strip Protoxylenm 1 mmExplanation / Answer
Answer 1: In src mutant endodermis and pericycle are not present.
Answer 2: On comparing figure 2 with figure 1 it can be easily concluded that after cortex in src mutant no endodermis and no pericycle is present. And the cells of protoxylem are also not arranged in a proper manner.
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