Everything you need to know about ribosomal RNA in microbial technology. Some of the questions are as follows:-
Q.1. What is rRNA?
Ans. The rRNA is ribosomal RNA of various sizes and forms the part of ribosomes. It comprises 90% of total RNA of the cell while the remainder part of the ribosomes comprises ribosomal proteins.
Q.2. Give types of rRNA found in bacterial and archaeal 70 S ribosomes.
Ans. Bacterial and archael 70 S ribosomes comprise 50 S and 30 S subunits. The 50 S subunit has 23 S rRNA and 5 S rRNA. The 30 S subunit has 16 S rRNA.
Q.3. Give types of rRNA found in eukaryotic 80 S ribosomes.
Ans. The 80 S ribosomes comprise 60 S and 40 S subunits. The 60 S ribosome contains 28 S rRNA and 5.8 S rRNA while the subunit 40 S possesses 18 S rRNA.
Q.4. What is 16 S rRNA?
Ans. The ribosomal subunits have several ribosomal rRNA molecules of different molecular weights, e.g., 30 S subunits in bacterial and archael cells possess 16 S rRNA.
Q.5. Give the use of 16 S rRNA sequence in microbial taxonomy.
Ans. No doubt rRNA analyses are poor indicators of species level differences. Nevertheless RNA sequencing has been used extensively in microbial taxonomy. The sequences of 5 S and 16 S rRNAs are isolated from 50 S and 30 S subunits respectively. Their occurrence and the source may be represented as
5 S rRNA Isolated form, → 50 S Subunit
16 S rRNA Isolated form, → 30 S Subunit
Purified radioactive 16 S rRNA can be analyzed by treating it with the enzyme Ti ribonuclease that cleaves it into fragments as represented here.
Purified radioactive 16 S rRNA Ti ribonuclease enzyme, → Fragments (each of 6 nucieotides).
The fragments so obtained are separated and all fragments composed of at least six nucleotides are sequenced. The sequence of corresponding 6S rRNA fragments from different bacteria is then compared using a computer and their association coefficient are calculated.
Q.6. What is polymerase chain reaction?
Ans. The polymerase chain reaction (PCR) is a method employed to amplify a specific DNA sequence in vitro by repeated cycles of synthesis using specific primers and DNA polymerase.
Q.7. Define a ribosome.
Ans. It is a cytoplasmic particle comprising ribosomal RNA and protein which is a part of the protein synthesizing machinery of the cell.
Q.8. What is a ‘signature sequence’?
Ans. These are short oligonucleotides of unique sequence found in 16 S rRNA of a particular group of prokaryotes. They are often found in defined regions of the 16 S rRNA molecules but are revealed when computer scans of two aligned sequences are carried out.