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(a) Differences between plasmid DNA and chromosomal DNA

Plasmid DNA		Chromosomal DNA
1. It is self replicating, DNA molecule found naturally in many bacteria and yeast. 2. It is not essential for normal growth and division and contains information for a few traits.		1. Chromosomal DNA present in chromosomes of all organisms. 2. It is essential for growth and division and contains information for all traits.

(b) Difference between exonuclease and endonuclease

Exonuclease This enzyme removes nucleotides from the terminals ,either from 5' or 3' ends of DNA molecules.

Endonuclease It cuts the DNA at specific position of nitrogen bases within  the length of DNA except the ends.

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(a) PCR—Polymerase Chain Reaction. It is the process in which multiple copies of the gene or segment of DNA of interest are synthesised in vitro using primers and DNA polymerase. It involves three basic steps; denaturation, annealing and extension (polymerisation).

 

(b) Restriction enzymesare  called “molecular scissors” or chemical scalpels. Restriction enzymes, synthesized by micro-organisms as a defence mechanism which can cleave double-stranded DNA at specific sites called recognition sequences. The recognition sequence is a palindrome, where the sequence of base pairs reads the same on both the DNA strands, when the orientation of reading is kept the same.

(c) Chitinase. are hydrolytic enzymes used  to degrade chitin . It is used to break the cell open to release DNA along with other macromolecules such as RNA, proteins, polysaccharides and also lipids.