What is genetic engineering ?

Genetic engineering is a technique for artificially and deliberately modifying DNA (genes) to suit human needs. It is used to change the genetic makeup of the cells by using Recombinant DNA technology 

Do eukaryotic cells have restriction endonucleases ? Justify your answer.

No, eukaryotic cells do not have restriction endonucleases. This is because the DNA of eukaryotes is highly methylated by a modification enzyme, called methylase. Methylation protects the DNA from the activity of restriction enzymes .These enzymes are present in prokaryotic cells where they help prevent the invasion of DNA by virus.

Explain briefly the following

(a) PCR (b) Restriction enzymes and DNA

(c) Chitinase.

(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.


From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size. How did you know ?

DNA molecules are bigger in size as compared to enzymes. Enzymes are proteins which are  synthesized from a small portion of DNA called genes therefore they are smaller than DNA molecules.

Describe briefly the following :

(a) Origin of replication (b) Bioreactor (c) Downstream processing

(a) Origin of replication (Ori).
1. It is a specific sequence of DNA bases, which  initiates replication.A prokaryotic DNA has normally a single oringin of replication, while eukaryotic DNA may have more than one. This sequence controls the copy number of linked DNA. An alien DNA for replication should be linked to the origin of replication

(b) Bioreactor are vessels in which raw materials are biologically converted into specific products using microbial, plant or human cells. It provides optimal conditions for achieving the desired product by providing optimum growth conditions, pH, substrate salts, vitamins, oxygen, etc.

(c) Downstream processing.are the series of processes which a genetically modified product undergoes before it is ready to be marketed. It generally involves processes like  separation and  purification.


What would be the molar concentration of human DNA in a human cell ? Consult your teacher.

Humans have 3 M of DNA per cell where M stands for molarity