Molecular Biology

Step 1: Understanding DNA bonds
Phosphodiester bonds (ester bonds) connect the phosphate group to the hydroxyl group of the sugar in DNA.
Hydrogen bonds occur between base pairs (A-T, G-C).
Glycosidic bonds link nitrogenous bases to the sugar.
Peptide bonds are found in proteins, not DNA.
Final Answer:

To solve the problem, we need to arrange the steps of the polymerase chain reaction (PCR) cycle in the correct order.

1. Understanding the PCR Cycle:
Polymerase chain reaction (PCR) involves a series of temperature-dependent steps to amplify DNA. The basic steps are:

• Denaturation (II): The DNA is heated to separate the two strands of the double helix.
• Annealing (IV): The temperature is lowered to allow primers to bind to the target DNA sequences.
• Extension (III): The DNA polymerase extends the primers, synthesizing new DNA strands.

2. Analyzing the Correct Order:
The PCR steps follow a specific order:
Denaturation (II) occurs first, where the DNA is separated into single strands.
Annealing (IV) comes next, where primers bind to the separated strands.
Extension (III) occurs last, where the DNA polymerase extends the primers to synthesize new DNA strands.

Final Answer:
The correct order of steps is (D) II - IV - III.