Molecular Biology

From which organism was Taq polymerase originally isolated, and what unique property makes it valuable in molecular biology?

• Escherichia coli; its ability to synthesize RNA.

• Thermus aquaticus; its stability at high temperatures.

• Saccharomyces cerevisiae; its role in fermentation.

• Homo sapiens; its function in DNA repair.

After DNA is cut into fragments by restriction enzymes, what type of bonds allow these fragments to re-anneal, forming recombinant DNA?

• Covalent bonds

• Ionic bonds

• Hydrogen bonds

• Peptide bonds

What is the main purpose of the Polymerase Chain Reaction (PCR) in molecular biology?

• To separate DNA fragments by size.

• To determine the exact sequence of DNA nucleotides.

• To amplify specific DNA sequences, creating many copies.

• To cut DNA at specific recognition sites.

What is the primary function of restriction enzymes in molecular biology, and what is their natural role in bacteria?

• To synthesize new DNA strands; to repair bacterial DNA.

• To join DNA fragments together; to facilitate bacterial conjugation.

• To cut DNA at specific sequences; to defend bacteria against viral infections.

• To separate DNA fragments by size; to regulate gene expression in bacteria.

What characteristic of DNA fragments primarily determines their migration distance through the gel matrix during gel electrophoresis?

• Their electrical charge

• Their nucleotide sequence

• Their molecular size

• Their chemical composition

Why do DNA fragments move towards the positive electrode in a gel electrophoresis setup?

• DNA molecules are positively charged.

• The gel matrix has a positive charge.

• DNA molecules are negatively charged.

• The buffer solution carries a positive charge.

Which of the following is NOT a required component for performing a Polymerase Chain Reaction (PCR)?

• DNA primers

• Taq polymerase

• Restriction enzymes

• Deoxynucleotides (A, C, T, G)

In DNA sequencing, what is the primary function of dideoxynucleotides (ddNTPs)?

• To initiate the replication process.

• To denature the DNA double helix.

• To terminate DNA strand elongation at specific bases.

• To amplify the DNA sample exponentially.