Question

e) Can you identify any wildtype (nonmutant) colonies in the figures? Explain your answer. f) Can you identify any standard (non-conditional) mutants in the figures? Explain your answer. g) Can you identify any conditional mutants in the figures? Explain your answer. 23°C mutant colony in which cells proliferate at the cooler, permissive temperature but fail to proliferate at the warmer, nonpermissive temperature 23°C colonies replicated onto two identical plates and incubated at two different temperatures mutagenized cells plated out in Petri dish grow into colonies at 23°C 36°C

Answer 1

e) The colonies, which can grow at both 23 degrees and 36 degrees C temperature, are considered as wild type. No mutation can be imparted in the cells, thus, they grow without any issue at both the temperatures. That is, no mutation means no modification of the sequence of amino acids, the proteins remain in the active state, and thus are considered wild type. Only wild type colonies can develop at both the temperatures, as both the temperature are favorable to them, and they exhibit no condition for developing.

f) On observing the given figure, one can conclude that a standard mutant may be present. The non-conditional mutant or standard mutant signifies that it possesses mutation, however, it does not rely upon any condition. Though the standard mutant cannot be determined by the replica plating. The standard mutant can be determined with the help of functional analysis or analysis of the gene sequence of the developed cells. It can be the case that the mutation may be neutral, so it may not influence the growth of the cell.

g) The colonies that grow at 23 degrees C, however, cannot grow at 36 degrees C and are considered mutant. With mutagen treatment, a missense mutation is presented into the cells, the sequence of amino acid get disoriented, the conformation of the protein is not in functional shape, therefore, the cells cannot grow at a higher temperature. This form of mutation is known as temperature-sensitive mutation or heat-sensitive mutation. This mutant cell loses the tendency to grow in the absence of permissible temperature, thus known as a conditional mutant. This kind of mutation may minimize the function of the gene products under a particular temperature that can be lethal for the cell.