Question

1.) The widespread misuse of antibiotics, in both humans and livestock, has led to widespread antibiotic resistance among bacterial strains that infect humans and other animals. Antibiotic resistance is a genetic trait, encoded by specific alleles that emerge through mutation. Do antibiotics cause the mutations that lead to resistance? Provide a full answer to this question using 2-3 complete sentences. 2.) Why is it said that the emergence of mutations is the result of who wins in a race between DNA repair and DNA replication? (Again, 2-3 full sentences at least.) 3.) Certain DNA sequences are especially prone to “strand slippage.” In your own words, give an account of how this phenomenon can lead to a specific genetic disease.

Answer 1

(a) Mechanism of bacterial resistance include three methods:

(i) Enzymatic degradation of Antibacterial drugs

(ii) Alteration of bacterial protein that are antimicrobial target

(iii) Change in membrane permeability

So, the mutation takes place in the bacterial protein which is not caused by the antibiotic but it is due to the environment and the bacteria itself for its better survival even in the presence of Antibiotics.

(b) The emergence of mutation is depend on the DNA repair and DNA replication. The mutation caused by the DNA repair gene cannot be revert back because the repairing mechanism itself is defective whereas mutation in DNA replication can be revert back because of the active response of the DNA repair mechanism.

(c) Strand slippage refers to the process that occurs during DNA replication. In this process, there is denaturation and displacements of DNA strands resulting in mispairing of complementary strands. Usually causes tandem repeats.

In Huntington's disease due to the replication slippage there is expansion in tandem repeats of HD gene. The tandem repeats in normal individual is 6-35 that expands to 36-121. It leads to formation of dysfunctional protein that shows damaging effect on Heart functions.