What are the four nucleotide bases found in DNA?
A.
Adenine, Thymine, Cytosine, Guanine.
B.
Adenine, Thymidine, Cytidine, Guanine.
C.
Adenosine, Thymine, Cytosine, Guanosine.
D.
Adenosine, Thymidine, Cytidine, Guanosine.
The Correct Answer and Explanation is:
The correct answer is A. Adenine, Thymine, Cytosine, Guanine.
Explanation:
DNA (deoxyribonucleic acid) is the molecule that carries genetic instructions in all living organisms. It consists of two long chains (polynucleotides) coiled around each other to form a double helix. Each chain is composed of a backbone made up of sugar and phosphate groups, with nitrogenous bases extending from this backbone. The sequence of these nitrogenous bases encodes genetic information.
The four nucleotide bases in DNA are:
- Adenine (A): Adenine is a purine base. In the DNA double helix, adenine forms hydrogen bonds with thymine. Adenine is crucial for the encoding of genetic information and is involved in the regulation of DNA replication and transcription.
- Thymine (T): Thymine is a pyrimidine base. It pairs specifically with adenine through two hydrogen bonds, which contributes to the stability of the DNA double helix. Thymine is unique to DNA; in RNA, thymine is replaced by uracil.
- Cytosine (C): Cytosine is another pyrimidine base. It pairs with guanine through three hydrogen bonds. This base-pairing is essential for maintaining the structural integrity of the DNA molecule and for accurate DNA replication.
- Guanine (G): Guanine is a purine base. It pairs with cytosine in the DNA double helix. The pairing between guanine and cytosine is stronger due to the three hydrogen bonds, which adds to the overall stability of the DNA structure.
Options B, C, and D include incorrect terms:
- Thymidine and Thymidine are not used in DNA. The correct term is Thymine.
- Cytidine and Guanosine are nucleosides, not nucleotide bases. They are composed of a base (cytosine or guanine) linked to a sugar (ribose or deoxyribose), but the base itself in DNA is Cytosine and Guanine.
In summary, the correct bases in DNA are Adenine, Thymine, Cytosine, and Guanine, which pair specifically to form the structure of DNA and ensure the accurate transmission of genetic information.