1. Tardigrade
  2. Question
  3. Biology
  4. How many of the following statements are TRUE? (i) 6 turns of B-DNA has 120 nucleotides. (ii) In prokaryotes, gene regulation generally occurs at transcriptional level. (iii) Operon concept was given by Jacob and Monod while working on yeast. (iv) The enzyme required for peptide chain synthesis is a ribozyme in bacteria and lies in 50S subunit. (v) A small segment of RNA synthesized during replication of DNA is Okazaki segment.

Q. How many of the following statements are TRUE?
(i) 6 turns of B-DNA has 120 nucleotides.
(ii) In prokaryotes, gene regulation generally occurs at transcriptional level.
(iii) Operon concept was given by Jacob and Monod while working on yeast.
(iv) The enzyme required for peptide chain synthesis is a ribozyme in bacteria and lies in 50S subunit.
(v) A small segment of RNA synthesized during replication of DNA is "Okazaki segment".

 2005  190 NTA AbhyasNTA Abhyas 2020Molecular Basis of Inheritance Report Error

Solution:

In prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression. In a transcription unit, the activity of RNA polymerase at a given promoter is regulated by interaction with accessory proteins, which affects its ability to recognize start sites. These regulatory proteins can act both activators (positively) and repressor (negatively). The functioning of operator depends upon the protein products.
Functional unit of DNA having a group of genes regulated by a single promoter is termed as operon. Operon holds the promoter, operator and the structural genes which express to produce the necessary protein Intron is not part of the operon. Lac operon is one of the most widely studied operon model. It was described by François Jacob and Jacques Monod in E. coli.
Protein synthesis is the process of making protein where ribosomes play an important role in its synthesis. A complex set of enzymes regulate the protein production process. One of the enzymes is peptidyl transferase which forms peptide bonds between amino acids in found on the 50S subunit of ribosome. It acts a ribozyme.
Short sequences of DNA formed discontinuously and later joined together by enzyme DNA ligase is called 'Okazaki' fragments. These form part of the lagging strand in the DNA replication process. Okazaki fragments were discovered by Japanese molecular biologists Reiji and Tsuneko Okazaki.
In B-DNA, each turn in it consists of 10 base pairs that is 20 nucleotides and thus 6 turns will have 120 nucleotides.