26. Which of the following nucleotides is not a component of DNA?
Answer: C
Uracil is not a component of DNA.
Uracil is the nucleotide that is not found in DNA; instead, it is a component of RNA. In DNA, the nucleotide thymine is used in place of uracil.
A) Adenine
Adenine is one of the four main nucleotides in DNA, pairing with thymine in the double helix structure. It is essential for forming the genetic code.
B) Thymine
Thymine is a crucial nucleotide in DNA, where it pairs with adenine. It is one of the four building blocks that make up the DNA structure, confirming its role as a DNA component.
C) Uracil
Uracil is not a component of DNA; it replaces thymine in RNA. This distinction is critical, as uracil does not participate in the structure or function of DNA, making this option correct.
D) Cytosine
Cytosine is one of the four primary nucleotides in DNA, pairing with guanine. It plays a significant role in the formation of the DNA double helix and is therefore a vital component of DNA.
Conclusion
Uracil is definitively not a component of DNA, as it is specifically found in RNA. All other options, adenine, thymine, and cytosine, are integral parts of the DNA structure, confirming that they do not represent the correct answer.