#bioinformatics

Plasma Membrane Proteins

Which experimental technique is commonly used to determine the number of transmembrane domains in a protein?

Prediction of membrane topology begins with hydropathy profiling visualizing hydrophobic potential along polypeptide. Kyte-Doolittle scale assigns each amino acid numerical value reflecting water to vapor transfer free energy: isoleucine four point five, valine four point two, leucine three point eight highly hydrophobic, arginine minus four point five highly hydrophilic. Sliding window average typically nineteen to twenty one residues equivalent to hydrophobic thickness smooths profile revealing peaks above threshold about one point six indicating membrane-spanning segments. Positive-inside r

Ref: Kyte and Doolittle, A Simple Method for Displaying Hydropathic Character, J Mol Biol 1982.

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MOLECULAR EVOLUTION

Neighbor-joining method constructs trees using:

Distance matrix reflects key principle in quiz on molecular evolution, where evolutionary mechanisms shape genetic variation and adaptation. In this context, Distance matrix aligns with experimental and theoretical evidence from population genetics, behavioral ecology and molecular phylogeny. Textbooks like Campbell Biology, Futuyma Evolution and Hartl Principles illustrate supporting data. Understanding why Distance matrix fits helps integrate natural selection, environment.

Ref: Li, Molecular Evolution, Neutral Theory and Molecular Clocks.

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MOLECULAR EVOLUTION

UPGMA is based on:

Distance similarity reflects key principle in quiz on molecular evolution, where evolutionary mechanisms shape genetic variation and adaptation. In this context, Distance similarity aligns with experimental and theoretical evidence from population genetics, behavioral ecology and molecular phylogeny. Textbooks like Campbell Biology, Futuyma Evolution and Hartl Principles illustrate supporting data. Understanding why Distance similarity fits helps integrate natural selection, environment.

Ref: Li, Molecular Evolution, Neutral Theory and Molecular Clocks.

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Sequencing

Which is used to align reads in NGS?

Next-generation sequencing instruments generate tens of millions of short reads that individually are too short for direct biological interpretation. Bioinformatics mapping uses algorithms like BWA, Bowtie2 or Minimap2 to align each read to a reference genome assembly of same species, finding best match position tolerating mismatches and indels. Successful alignment reveals coverage depth, variants and expression levels. Fluorescent scanners capture images, polyacrylamide gels were used for Sanger fragment sizing, pH meters are irrelevant. Reference genome mapping is therefore essential step c

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.

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Transcriptome analysis

Which of the following detects tandem repeats poorly?

Interphase FISH uses decondensed nuclear chromatin, where spatial resolution and signal coalescence are suboptimal. Tandem repeat clusters, being repetitive and often closely spaced, produce merged or diffuse fluorescent signals that are hard to quantitate and enumerate in interphase nuclei. Metaphase chromosomes provide condensed, linearly ordered targets where repeat arrays are linearly resolved. Microarray and SAGE interrogate sequence content differently. Hence, interphase FISH suffers reduced sensitivity and specificity for enumerating tandem repeats compared to metaphase FISH, which offe

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.

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Transcriptome analysis

What is the basic principle behind DNA microarrays?

DNA microarray performance depends on Watson-Crick base pairing between immobilized probes and fluorescently labeled target nucleic acids. Under controlled temperature and salt concentration, complementary sequences form stable duplexes, while mismatched sequences are removed during stringent washes. The resulting hybridization signal strength reflects thermodynamic stability and target concentration, permitting quantitative comparison across samples. PCR amplification, competitive binding unrelated to nucleic acid complementarity, and northern transfer principles describe separate techniques.

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.

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Transcriptome analysis

In DNA Microarrays, what does each spot represent?

A DNA microarray contains ordered microscopic spots, each printed with multiple identical probes complementary to a single transcriptional unit. Typically, probes correspond to a specific gene, EST, or predicted open reading frame. When fluorescently labeled cDNA or cRNA derived from samples hybridizes, intensity at each coordinate correlates with abundance of that gene's transcripts. Although a gene may contain multiple exons, array design aggregates exons under one gene identifier or multiple spots per exon in exon arrays. Spots do not represent individual primers, proteins, or isolated exon

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.

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Transcriptome analysis

Which invention is credited to Patrick O. Brown?

Patrick O. Brown, at Stanford University, introduced the concept of printing defined DNAs onto glass slides via robotic spotting in 1995. His laboratory demonstrated that differently labeled cDNAs from two samples could competitively hybridize to such arrays to quantify differential gene expression genome-wide. This innovation founded modern transcriptomics, enabling simultaneous monitoring of thousands of genes, shifting paradigm from single-gene northern blots. Fluorescence In Situ Hybridization, RNA sequencing, and CGH were developed by different groups focusing on cytogenetics and sequenci

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.

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