Molecular Genetics, Recombinant DNA & Genomic Technology MCQs

Ans. is 'a' i.e., Yellow green Fluorescein isothiocyanate (FITC) is a derivative of fluorescein used in wide-ranging applications including flow cytometry. FITC is the original fluorescein molecule functionalized with an isothiocyanate reactive group (-N=C=S), replacing a hydrogen atom on the bottom ring of the structure. This derivative is reactive towards nucleophiles including amine and sulfhydryl groups on proteins. FITC (fluorescein isothiocyanate) is a fluorochrome dye that absorbs ultraviolet or blue light causing molecules to become excited and emit a visible yellow green light. This emission ceases upon removal of the light causing the excitation.

Ans. is 'a' i.e., Transcribed from Nuclear DNA [Ref: Lippincott's Biochemistry 5thp.428;Fundamentals of Cytogenetics & Genetics (2010) p. 444] Mesenger RNA (mRNA) is formed by the process of 'transcription' from one of the strands of double stranded nuclear DNA and carries genetic information from the nuclear DNA to the cytosol where it is used as a template for protein synthesis. mRNA comprises only 5-10% of total cellular RNA. It carries the information (massage) from the nucleus to the ribosome. mRNA is synthesized in the nucleus as lieterogenous RNA (hn RNA)', which is processed into functional m RNA.

Option A: Systematic deletion mapping is genetic mapping technique that enables to determine the location of specific genes on chromosomes. Option B: DNAse I sensitivity assay used for discovering regulatory domains. This method maps discrete sites in the genome where the conformation of chromatin renders its DNA hypersensitive to cleavage by endonuclease DNAse I. Option C: Chromatin immunoprecipitation-sequencing (ChIP-seq) is used for simultaneous identification of all of the genomic sites bound by a given transcription factor under a given set of physiologic conditions Option D: Fluorescence in situ hybridization (FISH) is a molecular cytogenetic technique that uses fluorescent probes that bind to only particular parts of a nucleic acid sequence with high degree of sequence complementarity. Reference: Harper's illustrated biochemistry 32 nd edition CH 39 PN 447

Explanation: At 25 cycles the yield will be exactly half of that after 26 th as PCR amplification is exponential , following the formula: Number of copies = 2 n , where n is the number of cycles. Copies after 26 cycles = 2 26 Half of this amount = 2 26 / 2 = 2 26 x 2 -1 = 2 25 Therefore, the number of cycles needed to get half the copies is 25 cycles . Key Takeaways: Each PCR cycle doubles the number of DNA molecules. Therefore, one cycle less gives half the amount.

Explanation: Polymerase Chain Reaction ( PCR ) is a widely used molecular technique that amplifies specific DNA sequences. Once amplified, these DNA fragments can be sequenced accurately using methods such as Sanger sequencing or next-generation sequencing (NGS). Hence, PCR is central to determining DNA sequences. Explanation of Other Options: Flow cytometry (Option A): Used for cell sorting, counting, and analysis of cellular characteristics; not for sequencing DNA. FISH (Option B): Fluorescence In Situ Hybridization detects and localizes specific DNA sequences on chromosomes but does not determine nucleotide sequences. RFLP (Option C): Restriction Fragment Length Polymorphism identifies genetic variations based on fragment length differences after restriction enzyme digestion but is not a sequencing method. Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3883366/

Explanation: Natural selection is a process by which organisms better adapt to their environment and tend to survive and produce more offsprings. It is not a method for introducing recombinant DNA into a cell. Electroporation, microinjection and liposome-mediated delivery are all direct methods of introducing recombinant DNA into host cells by physically or chemically helping DNA enter the cell (electric pores, needle injection, or lipid fusion).

Explanation: Telomeres are repetitive DNA sequences located at the ends of linear chromosomes. Their primary role is to prevent the ends of chromosomes from being recognized as DNA breaks, thereby avoiding chromosomal fusion and ensuring the integrity and stability of the genome. Telomeres protect chromosomes from degradation and help maintain genomic stability during cell division.

Deficiency of vitamin B12 (cobalamin) leads to a deficiency in tetrahydrofolate and subsequently a deficiency of the dTMP required for DNA synthesis. Homocysteine and N5-methyltetrahydrofolate accumulate. Reference: Basic & Clinical Pharmacology, Fourteenth Edition By Bertram G. Katzung Pg no. 844