Concept explainers
Mutations are often considered harmful. Give an example of a mutation that would be beneficial to a microorganism. What gene would bear the mutation? How would the mutation alter the gene’s role in the cell, and what conditions would select for this mutant allele?
To identify: The gene that bears the mutation with an example of the mutation that is beneficial to the micro-organism.
Introduction: Alteration in the DNA sequence of the cell is known as a mutation. Various types of mutations found in the cell. Some mutations arise due to changes in the single base pair of nucleotides and the addition or deletion of a single nucleotide pair in the exon of the DNA sequence. These kinds of small changes are known as point mutations, which are associated with only a single base pair in a particular site of the DNA sequence. Larger mutations in the DNA sequence are less common. The larger mutations are larger insertions, deletions, duplications, translocations, and inversions of nucleotide sequences. Mutations often occur in two ways such as spontaneous mutations (which arise occasionally) and induced mutations (which arise from the exposure of mutagens).
Explanation of Solution
Generally, mutations are harmful to the cell because they affect proteins and phenotype of an organism. However, some mutations play a beneficial effect on microorganisms, for instance,mutation-induced antibiotic resistance in microorganisms. For example, a mutation in the rpsL gene induces resistance to the streptomycin (an antibiotic).
To describe: The condition that selects the mutant allele and how these mutations alter the gene’s role in the cell.
Explanation of Solution
The rpsL is considered as an important part of the ribosome. The interaction of streptomycin with the small subunit of the ribosome inhibits translation in microorganisms. Hence, mutations in the rpsL can reduce the binding efficiency of the ribosome to streptomycin. Therefore, the environment containing lethal concentrations of antibiotic streptomycin could be a very strong selective pressure for a mutation. Though the rpsL gene mutation produces a beneficial effect by inducing streptomycin resistance, it may affect other cellular function and protein synthesis.
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Chapter 16 Solutions
Prescott's Microbiology
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