Molecular Biology & Genetics

Molecular Biology & Genetics

α-oxidation of fatty acids takes place in

Phytanic acid containing branched methyl groups undergoes alpha-oxidation in peroxisomes. This pathway removes one carbon as formyl-CoA, converting phytanic acid to pristanic acid which then enters beta-oxidation. Peroxisomal localization protects mitochondria and explains Refsum disease accumulation when alpha-oxidation is defective.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 17 Fatty Acid Catabolism, and Stryer Biochemistry 9th Edition, Chapter 22, explains alpha-oxidation of branched fatty acids like phytanic acid occurs in peroxisomes producing pristanic acid, published by W.H. Freeman.

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Molecular Biology & Genetics

Thyroid hormone act through

Lipophilic thyroid hormones T3 and T4 diffuse across plasma membrane and bind high-affinity nuclear receptors. These receptors function as transcription factors belonging to steroid receptor superfamily, binding thyroid response elements to regulate basal metabolic rate, development and thermogenesis via gene expression modulation.

Ref: Berne and Levy Physiology, 7th Edition, Chapter 44 Thyroid Hormones, and Lodish Molecular Cell Biology 9th Edition, Chapter 16 Nuclear Receptors, describes thyroid hormone acting through nuclear receptors as transcription factors binding TRE, published by Elsevier Macmillan.

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Molecular Biology & Genetics

Allopurinol is used for the treatment of gout. It is an inhibitor of

Gout results from excess uric acid production via purine degradation. Xanthine oxidase catalyzes hypoxanthine to xanthine and xanthine to uric acid. Allopurinol, a purine analog, acts as suicide inhibitor of this enzyme, lowering urate levels and preventing monosodium urate crystal deposition.

Ref: Katzung, Trevor and Masters, Basic and Clinical Pharmacology, 14th Edition, Chapter 36 Anti-gout Drugs, and Goodman and Gilman Pharmacological Basis 13th Edition, explains allopurinol inhibits xanthine oxidase reducing uric acid formation for gout treatment, published by McGraw-Hill.

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Molecular Biology & Genetics

Cholesterol does not act as a precursor for

Cardiolipin, also called diphosphatidylglycerol, originates from phosphatidic acid via phosphatidylglycerol pathway in mitochondria and is not cholesterol-derived. Conversely cholesterol serves as precursor for steroid hormones including progesterone, cortisol, estradiol, testosterone and bile acids, but not glycerophospholipids like cardiolipin.

Ref: Berg, Tymoczko and Stryer, Biochemistry, 9th Edition, Chapter 26 Lipid Biosynthesis and Cholesterol Metabolism, explains cholesterol as steroid precursor for progesterone cortisol estradiol but not for cardiolipin which derives from phosphatidic acid, published by W.H. Freeman.

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Molecular Biology & Genetics

Which of the following type of enzyme inhibition is also called as end-product inhibition?

Accumulation of pathway end-product typically inhibits the first committed enzyme, preventing overproduction. This feedback inhibition represents allosteric regulation where final metabolite binds regulatory site, reducing flux. It efficiently conserves energy and metabolites, classic in amino acid biosynthesis like isoleucine inhibiting threonine deaminase.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 6 Enzyme Regulation, and Voet Biochemistry 4th Edition, Chapter 15 Regulation, describes feedback inhibition also called end-product inhibition where final product allosterically inhibits early pathway enzyme, published by Wiley Freeman.

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Molecular Biology & Genetics

Hot-start PCR is a modification of PCR. Which of the following is not corresponding to it?

Contrary to non-specific amplification, hot-start PCR minimizes primer-dimer and mispriming. By withholding Taq polymerase activity until denaturation temperature exceeds 90°C via antibody, wax barrier or chemical modification, it prevents extension at low temperatures, thus enhancing specificity and product yield, not generating spurious bands.

Ref: Dieffenbach and Dveksler, PCR Primer: A Laboratory Manual, 2nd Edition, Chapter Hot-start PCR Techniques, and Sambrook Molecular Cloning, describes hot-start modification preventing nonspecific products by activating polymerase only at high melting temperature, published by Cold Spring Harbor Laboratory Press.

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Molecular Biology & Genetics

What is the mode of action of exonuclease III?

Exonuclease III predominantly digests double-stranded DNA from blunt ends or 3'-recessed termini. It hydrolyzes phosphodiester bonds in the 3' to 5' direction releasing 5'-mononucleotides, while lacking activity on single-stranded DNA or 3' overhangs longer than four bases, useful for deletion cloning.

Ref: Lindahl, Jiricny and Wood, Biochemistry of Exonucleases in Molecular Biology of the Cell Alberts 6th Edition, Chapter 5 DNA Repair Enzymes, and Sambrook Molecular Cloning, explains exonuclease III acts on double stranded DNA in 3 to 5 direction, published by Cold Spring Harbor Press.

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Molecular Biology & Genetics

The name Alic Jeffery is associated with

Alec Jeffreys pioneered DNA fingerprinting at Leicester University by discovering variable number tandem repeat minisatellites. His technique uses multilocus probes recognizing hypervariable core sequences, creating individual-specific patterns that revolutionized forensic identification, paternity testing, and population genetics studies worldwide.

Ref: Jeffreys Alec, Nature Journal 1985 seminal papers on minisatellites, referenced in Strachan Human Molecular Genetics 5th Edition, Chapter 17 DNA Fingerprinting, and Hartl Essential Genetics, describes Jeffreys association with DNA fingerprinting VNTR probes, published by Garland Science Jones Bartlett.

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Molecular Biology & Genetics

P1 cloning vector allow cloning of DNA of the length of

Bacteriophage P1-derived cloning vectors accommodate large inserts due to phage head capacity. They package approximately 100 kilobase pairs, bridging lambda vectors and BACs. Cre-lox circularization and capacity for substantial genomic fragments make P1 vectors valuable for constructing physical maps and positional cloning.

Ref: Primrose, Twyman and Old, Principles of Gene Manipulation and Genomics, 8th Edition, Chapter 4 Cloning Vectors, explains P1 phage derived vectors allow cloning up to 100 kbp DNA due to headful packaging mechanism, published by Wiley-Blackwell.

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Molecular Biology & Genetics

Microbiosensors are based on

Microbiosensors often employ ion-sensitive field effect transistors where biological recognition events alter surface charge. Enzymatic conversion produces ions changing gate potential, modulating source-drain current. This ISFET principle allows miniaturized, rapid, label-free measurement of glucose, urea, or other metabolites clinically.

Ref: Bergveld, Sensors and Actuators B, and Turner Principles of Biosensors in Biotechnology textbook series, 3rd Edition, Chapter 4 Ion Sensitive Field Effect Transistor, describes microbiosensors based on ISFET measuring ion changes upon enzymatic reaction, published by Elsevier Oxford University Press.

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Molecular Biology & Genetics

Biochips are made up of

Biochips integrate semiconductor elements within protein scaffolds, creating bioelectronic interfaces. The protein framework provides biocompatibility and self-assembly while semiconducting molecules enable electron transfer, allowing sensitive detection of biomolecular interactions for diagnostics, drug screening, and nanoscale biosensing applications in modern research.

Ref: Vo-Dinh, Nanobiosensors and Biochips in Biomedical Nanotechnology Springer, and Ratner Biomaterials Science 4th Edition, Chapter on Biochips, describes biochips made of semiconducting molecules inserted into protein framework for biosensing, published by Springer Elsevier Academic Press.

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Molecular Biology & Genetics

Which protein moves the least from point of application of sample while electrophoresis

Serum protein electrophoresis separates proteins by charge and size at alkaline pH. Albumin migrates fastest toward anode due to high negative charge, while gamma globulins, being larger and less negatively charged, remain near application origin and thus move least, aiding myeloma diagnosis.

Ref: Harper's Illustrated Biochemistry, Rodwell et al., 31st Edition, Chapter 50 Plasma Proteins and Electrophoresis, and Lehninger, explains serum protein electrophoresis mobility where gamma globulin moves least due to low charge, albumin fastest, published by McGraw-Hill Lange.

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