6 public questions tagged with this topic.
Similarity in DNA sequences among diverse organisms supports the concept of common ancestry.
Ref: NCERT Class 12 Biology Chapter 6: Evolution Adaptive Radiation and Biological Evolution
Terminal inverted repeats TIRs are defining structural feature of DNA transposons consisting of short sequences at opposite ends that are reverse complements, typically 10-40 bp, sometimes containing subterminal transposase binding motifs. Inverted orientation allows single transposase dimer to simultaneously contact both ends bending DNA into paired-end complex aligning catalytic DDE residues for cleavage. Sequence conservation within repeats ensures specificity, while small asymmetries differentiate autonomous and non-autonomous families. Mutagenesis of repeats abolishes binding demonstrating essential cis role for mobilization. This principle illustrates essential molecular mechanisms governing replication fidelity and mutation fixation relevant for exam interpretation.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: Terminal Inverted Repeats in DNA Transposons
Sequencing human genome demonstrates almost 45 percent derives from transposable element remnants dominated by LINE-1 autonomous retrotransposons, Alu SINEs derived from 7SL RNA, SVA elements, and endogenous retroviruses. Most copies are truncated inactive fossils accumulated over millions of years, yet active LINE-1 subfamilies retain retrotransposition ability causing new germline insertions associated with disease. Massive repetitive content influences genome size, provides material for exonization, regulatory innovation, and ectopic recombination contributing to structural variation and evolutionary plasticity. This principle illustrates essential molecular mechanisms governing replication fidelity and mutation fixation relevant for exam interpretation.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: Human Genome TE Content 45 Percent
Hybridization stability depends on chemical composition and physicochemical environment. Guanine-cytosine pairs contain three hydrogen bonds versus two for adenine-thymine, and stronger base-stacking interactions, conferring higher thermodynamic stability and elevated melting temperature. Elevated monovalent cation concentration, such as high salt, stabilizes duplex by shielding electrostatic repulsion between negatively charged phosphate backbones. High temperature destabilizes mismatched duplexes but GC-rich sequences retain annealing due to greater enthalpy. Therefore combination of GC-rich sequence with high salt maintains most stable hybrid despite thermal stress, whereas AT-rich or low salt conditions favor dissociation.
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.
Expressed Sequence Tags are short sequences derived from cDNA clones representing expressed genes. The 5' EST contains coding portion and is relatively conserved across species because protein-coding constraints limit divergence, making it useful for ortholog identification and comparative genomics. The 3' EST corresponds more to 3' UTR, less conserved and more species-specific. SNPs represent single-base variations and VNTRs are tandem repeat copy-number variants, neither inherently coding nor necessarily conserved. Hence 5' ESTs provide cross-species coding information and functional annotation potential.
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.
5'-AAGCTT-3' is the scientifically accurate answer to this question. Within the study of DNA, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of 5'-AAGCTT-3' directly address what is being asked. Among the other options, 5'-GATTACA-3', 5'-AGTCGA-3', and 5'-CCGTAA-3' 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: Molecular Biology of the Gene, Watson et al., 7th Ed.
