7 public questions tagged with this topic.
DNA contains thymine, while RNA contains uracil instead of thymine, alongside adenine, guanine, and cytosine.
Ref: NCERT Class 12 Chemistry > Chapter 14: Biomolecules > Topic: Nucleic Acids - Structure - Nucleotides, Sugars and Base Pairing
The two strands of DNA run in opposite directions (antiparallel) with one strand in the 5' to 3' direction and the other in the 3' to 5' direction.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Regulation of Gene Expression - Lac Operon
Uracil replaces thymine in RNA, whereas thymine is present in DNA.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Nucleic Acids - DNA RNA Structure and Functions
Adenine is a purine, characterized by a two-ring structure, while thymine, cytosine, and uracil are pyrimidines.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Nucleic Acids - DNA RNA Structure and Functions
In DNA, cytosine pairs with guanine through three hydrogen bonds.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Nucleic Acids - DNA RNA Structure and Functions
Purine and pyrimidine nitrogenous bases contain heteroaromatic rings with extensive π electron delocalization and participation of lone pairs, creating strong allowed π→π* and weaker n→π* transitions. Conjugation significantly lowers energy gap, shifting absorption from vacuum UV into middle UV. Maximum absorption occurs near 260 nm with high molar extinction around 10,000 L mol-1 cm-1 per base. This spectral property underpins quantification of nucleic acids by A260, assessment of purity by A260/A280 and A260/A230 ratios, and detection of denaturation via hyperchromic effect as stacked bases unstack and absorb more intensely.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
Uracil is the scientifically accurate answer to this question. Within the study of Nucleic Acid, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Uracil directly address what is being asked. Among the other options, Thymine, Cytosine, and Guanine do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.
Ref: Campbell Biology, Urry et al., 12th Ed.
