Short Notes On Enzymes of rDNA Technology, Download PDF!

By Astha Singh|Updated : January 19th, 2023

Are you an Aspirant of CSIR-NET and looking for some short and reliable notes for Life Sciences to strong your base for preparations? We have got you covered!

Candidates preparing for their CSIR NET exam can really make their preparation journey easier with the help of some reliable study notes that cover the topics in the most simple way. We at BYJU'S Exam Prep have come up with the idea of providing short notes on Enzymes of rDNA Technology, which comes under the Methods Of Biology section of the Life Science syllabus. 

The short note on Enzymes of rDNA Technology is developed by our experienced subject-matter experts to provide you with the most standard and authentic set of study materials to be focused upon. The students need the best resources for their preparation to clear the CSIR NET examination, Here are the most reliable study Notes to make the topics easier for you and also help you to save your time for the preparations for the upcoming CSIR-NET 2023 exam.

Short Notes On Enzymes of rDNA Technology


Enzymes used in rDNA Technology

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DNA ligase
DNA ligase is isolated from E.coli and Bacteriophage commercially and used in recombinant DNA technology. The enzyme DNA ligase joins the DNA fragments with a cloning vector. DNA ligases can form a phosphodiester bond at a single-strand break in DNA, a reaction between a 3′-OH group and a 5′-monophosphate.

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Reverse transcriptase

RT is used to synthesize complementary strands (cDNA) from mRNA template. It is also known as RNA-dependent DNA polymerase. It is isolated from a retrovirus.

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Restriction endonuclease

Restriction endonuclease enzymes recognize and cut DNA strands at specific sequences called restriction sites. These enzymes are isolated from a wide variety of microorganisms. Endonuclease enzymes degrade foreign genomes when they enter a microbial cell but the host cell's own DNA is protected from its endonuclease by methylation of bases at the restriction site. There are 3 types of restriction endonuclease:

  1. Type I Restriction endonuclease - It has both methylation and endonuclease activity. It requires ATP to cut the DNA. It cuts DNA about 1000bp away from its restriction site. For example EcoKI.
  2. Type II Restriction endonuclease - It does not require ATP to cut DNA. It cuts DNA at the restriction site itself. For example, EcoRI, Hind III
  3. Type III Restriction endonuclease - It requires ATP to cut DNA. It cuts DNA about 25 bp away from the restriction site. For example, Sty

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Terminal transferase

It is the enzyme that converts the blunt end of DNA fragments into a sticky end. If the restriction enzyme cuts DNA forming blunt ends, then efficiency of ligation is very low. So the enzyme terminal transferase converts the blunt end into a sticky end. Terminal transferase enzymes synthesize short sequences of complementary nucleotides at free ends of DNA, so that the blunt end is converted into a sticky end.

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Nuclease

The enzyme nucleases hydrolyze the phosphodiester bond on the DNA strand creating the 3’-OH group and 5’-P group. It usually cut DNA on either side of distortion caused by thymine dimers or intercalating agents. The gap is filled by DNA polymerase and the strand is joined by DNA ligase. Nucleases are of two types; endonuclease and exonuclease.

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DNA polymerase

DNA polymerase is a complex enzyme that synthesizes nucleotides complementary to template strands. It adds nucleotide to free the 3′ OH end and help in the elongation of the strand. It also helps to fill gaps in double-stranded DNA. DNA polymerase-I isolated from E. coli is commonly used in gene cloning. Taq polymerase isolated from Thermus aquaticus is used in PCR.

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Ribonuclease-H (RNase H)

RNase-H removes mRNA from DNA-RNA heteroduplex and that mRNA is used to synthesize cDNA. It is isolated from retrovirus.

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