A-Which of the following is NOT one of the steps required to clone a piece of DN

Question

A-Which of the following is NOT one of the steps required to clone a piece of DNA using a plasmid vector?
1. Cut a vector and a DNA insert with a specific restriction enzyme to create complementary "sticky ends."
2. Isolate DNA fragments by gel electrophoresis.
3. Ligate insert DNA and a vector with similar sticky ends together.
4. Transform ligated pieces of DNA into E. coli.
5. Select the plasmid vector that has replaced its origin of replication with insert DNA.

B-A representative genomic library of an organism's DNA fragments results from the use of
1. DNA ligase joining multiple types of vectors.
2. partial digestion with frequently cutting restriction endonucleases.
3. many pieces of recombinant DNA from several different types of organisms.
4. viruses that cleave the DNA into random pieces.

C-One of the most useful methods for identifying a specific DNA sequence is
1. the Southern blot.
2. the Western blot.
3. magnetic resonance imaging.
4. the Eastern blot.
5. thin-layer chromatography.

Explanation / Answer

A)

The correct answer is option 5.

5. Select the plasmid vector that has replaced its origin of replication with insert DNA.

For cloning a piece of DNA using plasmid vector the following steps are followed:

Hence, the option 5 is not included in the process of cloning a DNA using a plasmid vector.

B)

The correct answer is option 2.

2. partial digestion with frequently cutting restriction endonucleases.

The construction of genomic library is done by the digestion of organism's DNA by using restriction enzymes. The fragments obtained through restriction digestion are then ligated into the vector and transformed into the host. When DNA is digested partial digestion is preferred so that the DNA is not cut at all restriction sites, so that large fragments are forments are formed.

C)

The correct answer is option 1.

1. the Southern blot.

The southern blot is used to blot the DNA separated in gel electrophoresis to a membrane of nitrocellulose. After the binding it can be detected by using probes, which are specific to the target sequence. The western and eastern blots are used for detection of proteins.

Therefore, the Southern blot is one of the most useful methods for identifying a specific DNA sequence.

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