Genetics And Evolution

Step 1: Use Michaelis–Menten equation.
Step 2: Substitute values.
Step 3: Conclusion.
The reaction velocity is 1 nM s .

Step 1: Use exponential growth formula.
Population increases from So number of doublings: Step 2: Use value .
Step 3: Total time = 5 hours = 300 minutes.
Step 4: Conclusion.
Thus, the doubling time ≈ 18.1 minutes.

Step 1: Understand plasmids.
Plasmids are extrachromosomal, circular DNA molecules in bacteria. They frequently carry genes that provide a selective advantage to the host cell.
Step 2: Identify the key function.
The most common genes carried on plasmids are R-plasmids, which provide resistance to antibiotics. These genes help bacteria survive antibacterial agents by neutralizing or pumping out drugs.
Step 3: Evaluate options.
(B) and (C) may occur but are not the primary or defining features of plasmids. (D) refers to conjugation, facilitated by F-plasmids, but resistance genes are the most common association.
Step 4: Conclusion.
Thus, plasmid genes are best associated with antibiotic resistance.

Step 1: Understand the trp operon.
The trp operon is a negatively controlled repressible operon. When tryptophan levels are high, tryptophan acts as a corepressor.
Step 2: Evaluate each statement.
(A) Correct — It is indeed a negatively controlled repressible operon.
(B) Incorrect — Tryptophan activates the repressor, not inactivates it.
(C) Incorrect — Tryptophan represses the operon; it does not induce it.
(D) Correct — The Trp–repressor complex binds to operator to stop transcription.
Step 3: Conclusion.
Thus, statements (B) and (C) are incorrect.