NEET Practice Questions (MCQs) with Answers & Solutions

In DNA replication, the primer is a small ribonucleotide polymer (o2). Primers are short RNA sequences that provide a starting point for DNA synthesis. They are synthesized by the enzyme primase and are necessary for DNA polymerases to begin adding DNA nucleotides.

Nonsense codons, also known as stop codons, are sequences in the genetic code that do not code for an amino acid and signal the termination of protein synthesis. When the ribosome encounters one of these codons (UAA, UAG, or UGA), it terminates translation, releasing the newly synthesized polypeptide chain. This is crucial for ensuring proteins are made to the correct length and function properly.

DNA Polymerase I has a 3' to 5' exonuclease activity that allows it to proofread and correct errors in DNA replication. When a wrong base is inserted, the enzyme can remove the incorrect nucleotide and replace it with the correct one, ensuring high fidelity during DNA replication.

Ribonuclease P and Peptidyl transferase are both ribozymes, which are RNA molecules with enzymatic activity. Ribonuclease P is involved in tRNA processing, while Peptidyl transferase is a component of the ribosome responsible for forming peptide bonds during protein synthesis.

Translation is the process by which the genetic code carried by mRNA is decoded to produce the specific sequence of amino acids in a polypeptide chain. The steps involved in translation are Initiation, Elongation, and Termination. Replication is the process of copying DNA, not a step of translation.

Aminoacyl-tRNA synthetase is an enzyme that attaches the appropriate amino acid onto its tRNA. This process is known as 'charging' or 'aminoacylation' of the tRNA. Therefore, the enzyme facilitates the adoption of amino acids by a tRNA molecule.

A gene consists of several regions including a promoter, which is the binding site for RNA polymerase to initiate transcription; initiation and termination sites, which mark the beginning and end of transcription; and the coding sequence, which is the part of the gene that is transcribed into mRNA and then translated into a protein. Therefore, all the mentioned components are part of a gene.

The enzymes needed for the catabolism of lactose in E. coli include β-galactosidase, permease, and transacetylase. β-galactosidase breaks down lactose into glucose and galactose, permease facilitates the entry of lactose into the cell, and transacetylase is involved in the removal of toxic byproducts of lactose metabolism.

An operon is a functioning unit of genomic DNA that contains a cluster of genes under the control of a single promoter. It contains a regulator gene, promoter gene, operator gene, and structural genes. The regulator gene produces a repressor protein that can bind to the operator region to control the transcription of the structural genes.