Molecular Basis of Inheritance MCQs

George Gamow (a physicist) proposed that the genetic code must be a triplet. Har Gobind Khorana synthesized RNA molecules (homopolymers and copolymers) chemically. Marshall Nirenberg developed a cell-free system for protein synthesis. Severo Ochoa discovered the enzyme Polynucleotide Phosphorylase for template-independent RNA synthesis,,.

VNTR (Variable Number of Tandem Repeats) is a mini-satellite used as the basis for fingerprinting. A Probe is a radioactive single-stranded DNA used to hybridize with the target sequence. Southern Blotting is the transfer of DNA from gel to a membrane. Electrophoresis separates DNA fragments based on size,,,.

mRNA acts as the template or messenger for protein synthesis. tRNA acts as an adapter molecule that reads the code and brings amino acids. rRNA plays a structural and catalytic (ribozyme) role in the ribosome. hnRNA (Heterogeneous Nuclear RNA) is the precursor to mRNA found in eukaryotes,,,.

In eukaryotes, RNA Polymerase I transcribes large rRNAs (28S, 18S, 5.8S). RNA Polymerase II transcribes hnRNA, which is processed into mRNA. RNA Polymerase III transcribes tRNA, 5S rRNA, and snRNAs. This can be remembered with the mnemonic "RaMeT" (I-rRNA, II-mRNA, III-tRNA).

Charging or aminoacylation is the activation of amino acids and binding to tRNA. Initiation involves the binding of the small ribosomal subunit to the mRNA (Shine-Dalgarno or Cap). Elongation involves the formation of peptide bonds, catalyzed by the ribozyme (23S rRNA). Termination occurs when Release Factors bind to the Stop codon,,,.

Degenerate means that some amino acids are coded by more than one codon (e.g., Leucine). Unambiguous means a specific codon codes for only one specific amino acid. Universal means the code is shared by nearly all organisms. Comma-less means the code is read contiguously without pauses,,,.

Helicase unzips the DNA helix by breaking hydrogen bonds. Topoisomerase relieves the tension/supercoiling ahead of the fork. Primase synthesizes the RNA primer needed to start replication. DNA Ligase joins the discontinuous Okazaki fragments,,,.

The 2D structure of tRNA resembles a Clover-leaf. The 3D structure resembles an Inverted L. The Acceptor Arm (3-prime end) binds to the amino acid. The Anticodon loop contains the sequence that reads the mRNA codon,.

Griffith described the Transforming Principle. Hershey and Chase provided unequivocal proof that DNA is the genetic material. Meselson and Stahl proved semi-conservative replication in E. coli using N-15. Taylor and colleagues proved semi-conservative replication in eukaryotes (Vicia faba) using radioactive thymidine,,,.

Capping involves adding Methyl Guanosine Triphosphate to the 5-prime end. Tailing involves adding Adenylate residues (Poly-A tail) to the 3-prime end. Splicing is the removal of non-coding Introns. Exons are the coding sequences that are retained in the mature mRNA,,.