Question

Describe one example of cellular (either cells within a multicellular organism or unicellular organisms) where population genetics involved in survival of the cell type through at least one mechanism.

Answer 1

Answer: One example of a cell survival mechanism of unicellular organisms such as bacteria where population genetics is involved, is the Stress-induced mutation that helps their survival in stressful conditions.

It has been found that once exposed to stress, a wide variety of unicellular organisms, as well as eukaryotes, undergo an increased rate of mutation. This type of mutations can again be classified into two categories - direct and indirect.

In the first scenario, the toxic chemical or agent has a direct effect on the cellular DNA, enzymes or other mechanisms that causes the increased mutation rate(often called Stress Associated Mutagenesis or SAM) and consequently acts as a mechanism for positive selection of that particular population. So, the population survives and thrives.

In the second case, the presence of stress can affect the cells indirectly in a way that alters the gene expression with increased mutation rates. This may result in the synthesis of error-prone DNA polymerase or altered DNA repair enzymes etc.( these mechanisms are often called Stress-Induced Mutagenesis). Due to the occurrence of these altered mechanisms now the bacterial population(or some members of the population) are now resisting the stress that is present. And as a result of that, the population survives.

Due to these mechanisms, Natural Selection will favor the population with beneficial mutations, better compatibility i.e. the population which is well-adapted to the current condition. So, over time these stress resistance mechanisms may be favored in a certain population. This selection may vary among different populations as well as populations in different geographical regions.

example: one example of such error-prone DNA polymerase expressed in stress condition is "Y-family DNA polymerase" that is class of highly mutagenic DNA-Pol IV that carry out post-lesion DNA synthesis.