Molecular basis of inheritance
Read the following passage carefully and answer the given questions.
In bacteria, since the mRNA does not require any processing to become active, and also since transcription and translation take place in the same compartment, many times the translation can begin much before the mRNA is fully transcribed. Translation refers to the process of polymerisation of amino acids to form a polypeptide. The order and sequence of amino acids are defined by the sequence of bases in the mRNA. In lac operon, a polycistronic structural gene is regulated by a common promoter and regulatory genes. Such arrangement is very common in bacteria and is referred to as operon. 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 in turn regulated by interaction with accessory proteins, which affect its ability to recognise start sites. These regulatory proteins can act both positively and negatively. DNA from every tissue of an individual show the same degree of polymorphism, they become very useful identification tool in forensic applications like DNA fingerprinting.
The process of removing introns and joining the exons in a defined order is known as -
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Splicing
In eukaryotes the first RNA copy of a gene, the hnRNA, contains both exons and introns and is not functional. It is processed in three ways before it leaves the nucleus.
(1) Splicing — Correct. In splicing, the introns are removed and the exons are joined in a defined order.
(2) Capping — Incorrect. In capping, an unusual nucleotide (methyl guanosine triphosphate) is added to the 5′ end of the hnRNA.
(3) Tailing — Incorrect. In tailing, 200-300 adenylate residues are added at the 3′ end, without a template.
(4) Polyadenylation — Incorrect. This is another name for tailing, the adding of the adenylate residues.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Types of RNA and the Process of Transcription – …
