Question

You have discovered a new strain of peach that is larger, sweeter and juicier. A karyotype reveals that it is tetraploid. Describe one way in which this new peach may have been generated. Use drawings if necessary.

Answer 1

Ans: Multiple approaches have been developed to generate tetraploid cells in vitro for pruduction of peach that is larger, sweeter and juicier. For production of tetraploid peach we can use dihydrocytochalasin B, which disrupts actin polymerization and thus causes cytokinetic cleavage furrow regression, cytokinesis failure, and tetraploidy. This compound does not disrupt mitotic spindle assembly or the efficiency of chromosome segregation, and does not produce DNA damage. DCB is a reversible drug that can be washed from cells, thus enabling the inhibition of cytokinesis during only a single cell cycle. This is a major benefit over knocking out or knocking down the expression of genes essential for cytokinesis, which will induce repeated cytokinesis failures. To generate tetraploid cells:

1. We should dilute DCB as required and add the growth medium containing DCB to each of the cells plated .
2. Incubate the cells in DCB for 16 h in a 37°C tissue culture incubator It should be noted that since DCB disrupts the actin cytoskeleton, the morphology of the cells will be dramatically and visibly altered: the cells will have ruffled edges and will be less spread on the tissue culture dish.
3. Aspirate the medium and gently rinse the cells with sterile PBS.
4. Wash the cells 5 times (5 min each time) in pre-warmed growth medium. These washes are essential to completely remove residual DCB from the cells. The DCB-treated cells should flatten out and assume a normal looking morphology immediately following the completion of these washes. At this point, may be ~40–60% of the cells should be visible as binucleated tetraploids under a phase contrast microscope.