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Question
The ends of DNA fragments are sticky due to
The ends of DNA fragments are sticky due to
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Solution
The correct option is C unpaired bases
Sticky end is a fragment of DNA produced by a staggered cut using restriction enzymes, in which the terminal portion has a stretch of unpaired bases. Examples include EcoR I, Hind III, BamH I etc.
Formation of sticky ends is as follows:
- Restriction enzymes break the phosphodiester bond between two specific adjacent nucleotides of a strand.
- The restriction enzyme cuts DNA at one end of the sequence, between two bases on the same strand, then cuts on the opposite end of the complementary strand in the same way.
- This results in the formation of two single stranded ends of DNA containing few nucleotides without any complementary bases. These ends are called sticky ends.
- When complementary sticky ends of DNA fragments meet, hydrogen bonds are formed between the complementary bases which results in annealing of the ends of the fragments.
Pictorial representation of the formation of sticky ends
Endonucleases are enzymes that cleave DNA at any point within the DNA strand but not at the ends.
For example, restriction endonucleases help in cutting the vector and the DNA of interest, so that the DNA of interest can be inserted into the vector to form rDNA.
The substitution of an atom or group by a methyl group is called free methylation. It regulates gene expression by inhibiting the binding of transcription factors to DNA.
Heat shock method is one of the most common methods for making the bacterial cells competent for transformation. In this method bacterial cells are treated with divalent ions (Ca2+) followed by a brief heat shock.
Hence the correct option is
a. unpaired bases
Sticky end is a fragment of DNA produced by a staggered cut using restriction enzymes, in which the terminal portion has a stretch of unpaired bases. Examples include EcoR I, Hind III, BamH I etc.
Formation of sticky ends is as follows:
- Restriction enzymes break the phosphodiester bond between two specific adjacent nucleotides of a strand.
- The restriction enzyme cuts DNA at one end of the sequence, between two bases on the same strand, then cuts on the opposite end of the complementary strand in the same way.
- This results in the formation of two single stranded ends of DNA containing few nucleotides without any complementary bases. These ends are called sticky ends.
- When complementary sticky ends of DNA fragments meet, hydrogen bonds are formed between the complementary bases which results in annealing of the ends of the fragments.
Endonucleases are enzymes that cleave DNA at any point within the DNA strand but not at the ends.
For example, restriction endonucleases help in cutting the vector and the DNA of interest, so that the DNA of interest can be inserted into the vector to form rDNA.
The substitution of an atom or group by a methyl group is called free methylation. It regulates gene expression by inhibiting the binding of transcription factors to DNA.
Heat shock method is one of the most common methods for making the bacterial cells competent for transformation. In this method bacterial cells are treated with divalent ions (Ca2+) followed by a brief heat shock.
Hence the correct option is
a. unpaired bases
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