The correct answer is option 3: cells having similar genetic constitution. A clone refers to a group of cells or organisms that have identical or nearly identical genetic information. In the case of a colony, it refers to a group of cells that are derived from a single parent cell and have the same genetic makeup. Therefore, all the cells in a clone have a similar genetic constitution. Option 1, cells having different shapes, is incorrect because clone cells typically have the same shape. Option 2, cells having similar shape, is also incorrect as shape is not a defining characteristic of a clone. Option 4, cells having different genetic constitutions, is incorrect as clones have identical or nearly identical genetic information.