Construction of a recombinant, DNA involves (A) cleaving of a recombinant DNA involves with 'endonuclease' alone (B) cleaving DNA segments with 'endonuclease' and rejoining them with 'ligase' (C) cleavig DNA segments with 'ligase' and rejoining them with 'endonuclease' (D) cleaving and rejoining DNA segments with 'ligase' alone

Options

A. cleaving of a recombinant DNA involves with 'endonuclease' alone
B. cleaving DNA segments with 'endonuclease' and rejoining them with 'ligase'
C. cleavig DNA segments with 'ligase' and rejoining them with 'endonuclease'
D. cleaving and rejoining DNA segments with 'ligase' alone

Answer

To construct recombinant DNA, the following steps are involved:

1. **Cleaving DNA Segments**: The first step in constructing recombinant DNA is to cleave or cut the DNA segments. This is done using specific enzymes known as restriction enzymes or endonucleases. These enzymes recognize specific sequences in the DNA and cut it at those sites, resulting in DNA fragments.

2. **Rejoining DNA Segments**: After the DNA segments have been cleaved, the next step is to rejoin these fragments. This is accomplished using another enzyme called ligase. Ligase facilitates the joining of the DNA fragments by forming phosphodiester bonds between the sugar and phosphate backbone of the DNA.

3. **Formation of Recombinant DNA**: The combination of cleaving and rejoining DNA segments results in the formation of recombinant DNA (rDNA), which consists of DNA from two or more different sources.

4. **Amplification and Use**: Once the recombinant DNA is constructed, it can be amplified and replicated to produce desired products, such as insulin or other proteins.

Based on the above steps, the correct answer to the question is:
**(B) cleaving DNA segments with 'endonuclease' and rejoining them with 'ligase'.**