2
Question
Study the following flowchart and identify the enzymes used in steps I and II.
Study the following flowchart and identify the enzymes used in steps I and II.
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Solution
The correct option is B EcoR I and DNA ligase
The flowchart given in the question illustrates the steps involved in the creation of a recombinant DNA (rDNA) molecule. Recombinant DNA is an artificial DNA created through the combination of DNA molecules from different biological sources that are not normally associated with each other. Restriction endonucleases and DNA ligases are two of the many types of enzymes required for the creation of rDNA.
Restriction enzymes are a type of endonucleases that cleave phosphodiester bonds between consecutive nucleotides within or near to specific DNA sequences that they identify. These identifiable sequences are known as recognition sequences that are usually palindromic in nature.
EcoR I is a restriction endonuclease that recognises the base sequence 5’ GAATTC 3’ in the DNA double strand and makes the cuts between G and A. It results in the formation of DNA fragments with single strand overhangs called sticky ends.
DNA ligase is an enzyme used to catalyze the formation of phosphodiester bonds between deoxyribonucleotides. The fragments formed by the action of restriction endonucleases are joined by the enzyme DNA ligase that results in the formation of a recombinant DNA molecule.
The given figure illustrates that EcoR I makes the cuts and DNA ligase joins the fragments of DNA.
Exonucleases cleave phosphodiester bonds between consecutive nucleotides at their terminal ends (either 5’ or 3’), one nucleotide at a time.
The first restriction endonuclease isolated was Hind II. It was isolated from Haemophilus influenzae. It recognises a specific sequence of 6 base pairs.
The flowchart given in the question illustrates the steps involved in the creation of a recombinant DNA (rDNA) molecule. Recombinant DNA is an artificial DNA created through the combination of DNA molecules from different biological sources that are not normally associated with each other. Restriction endonucleases and DNA ligases are two of the many types of enzymes required for the creation of rDNA.
Restriction enzymes are a type of endonucleases that cleave phosphodiester bonds between consecutive nucleotides within or near to specific DNA sequences that they identify. These identifiable sequences are known as recognition sequences that are usually palindromic in nature.
EcoR I is a restriction endonuclease that recognises the base sequence 5’ GAATTC 3’ in the DNA double strand and makes the cuts between G and A. It results in the formation of DNA fragments with single strand overhangs called sticky ends.
DNA ligase is an enzyme used to catalyze the formation of phosphodiester bonds between deoxyribonucleotides. The fragments formed by the action of restriction endonucleases are joined by the enzyme DNA ligase that results in the formation of a recombinant DNA molecule.
The given figure illustrates that EcoR I makes the cuts and DNA ligase joins the fragments of DNA.
Exonucleases cleave phosphodiester bonds between consecutive nucleotides at their terminal ends (either 5’ or 3’), one nucleotide at a time.
The first restriction endonuclease isolated was Hind II. It was isolated from Haemophilus influenzae. It recognises a specific sequence of 6 base pairs.
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