Macmillan Learning The process by which two complementary nucleic acid strands base-pair to form a double-stranded structure is called
A recombination.
B freezing.
C annealing.
D ligation.
E supercoiling.
The correct answer and explanation is:
The correct answer is C) annealing.
Annealing refers to the process by which two complementary nucleic acid strands (such as DNA or RNA) base-pair with each other to form a double-stranded structure. This occurs when the temperature is lowered in a solution of single-stranded nucleic acids, allowing them to re-form the double helix by complementary base pairing, i.e., adenine pairs with thymine (in DNA), and cytosine pairs with guanine.
This process is crucial for various biological and laboratory processes. For example, in DNA replication, the two strands of DNA must separate, and then they can “anneal” back together with the help of enzymes like DNA polymerase. In laboratory techniques like polymerase chain reaction (PCR), the annealing step is a critical phase where primers (short pieces of single-stranded DNA) bind to their complementary sequences on the target DNA, allowing for the replication of the desired region.
Here is why the other options are incorrect:
- A) Recombination refers to the process by which genetic material is exchanged between different molecules, leading to genetic variation.
- B) Freezing is a physical process where molecules slow down due to a drop in temperature; it is not related to the pairing of nucleic acid strands.
- D) Ligation is the process of joining two strands of DNA by forming a phosphodiester bond, typically carried out by the enzyme DNA ligase. It does not involve base pairing of complementary strands.
- E) Supercoiling refers to the coiling of a DNA molecule in a more compact form, which happens to relieve tension during DNA replication and transcription but is not related to base-pairing or annealing.
Thus, annealing is the correct term for the base-pairing process that forms a double-stranded nucleic acid structure.