cuts at a specific site in DNA.

combines lagging pieces of DNA.

helps in unwinding of DNA strand.

Gene gun is a method used in recombinant DNA technology to introduce the foreign DNA fragment into host cells. This method is also called biolistics that is suitable for plants. In this method, the host cells are bombarded with high-velocity micro-particles of gold or tungsten that is coated with foreign DNA. This method helps to transform plant cells without using a vector.

What is recombinant DNA technology? How is recombinant DNA prepared by using restriction enzymes? Describe briefly with the help of diagram.

Recombinant DNA (rDNA) technology is the technique of manipulating the genetic makeup of an organism to introduce a desirable gene in it and produce a new phenotype. Recombinant DNAs are prepared by a technology that involves specific enzymes to cut and paste together DNA sequences of interest. This technique was first proposed by Peter Lobban, a student of Stanford University but it became famous only after Stanley Cohen and Herbert Boyer (1972) could successfully link an antibiotic resistance gene with the plasmid of Salmonella typhimurium then cloned it in Escherichia coli . An important tool in rDNA technology is the restriction enzymes. Restriction endonuclease is also referred to as restriction enzyme or molecular scissors. These are proteins that are produced by bacteria that cleave DNA at specific sites along the molecule. Each restriction enzyme recognises a short, specific sequence of nucleotide bases. These are palindromic sequences. These regions are called recognition sequences and, are randomly distributed throughout the DNA. When the enzyme finds these sequences, they make a double-stranded cut near the restriction sites. The two types of cuts are done by restriction enzymes, the sticky ends and the blunt cuts. Sticky ends have single-stranded over-hanging ends, while the blunt cuts straight down the middle of a target sequence and leaves no overhang. Examples: Eco RI, Hin d II, etc. Eco RI is obtained from a bacterium, E coli.

Describe gene cloning.

Gene cloning is defined as the process of formation of an exact sequence of DNA or genes to make multiple copies of it. These multiple identical copies are called clones. It is also known as molecular cloning. Stanley Cohen and Herbert Boyer discovered the methods of creating a type of artificial DNA called recombinant DNA. A gene is separated and ligated to a vector like plasmid. The recombinant plasmid is introduced into a plasmid free bacterium. The transformed bacterium is made to multiply and each bacterium consists of copy of the gene.

Describe restriction enzyme.

Restriction endonuclease is also referred to as restriction enzyme or molecular scissors. These are proteins that are produced by bacteria that cleave DNA at specific sites along the molecule. Each restriction enzyme recognises a short, specific sequence of nucleotide bases. These regions are called recognition sequences and, are randomly distributed throughout the DNA. When the enzyme finds these sequences, they make a double-stranded cut near the restriction sites. The two types of cuts are done, the sticky ends and the blunt cuts. Sticky ends have single-stranded over-hanging ends, while the blunt cuts straight down the middle of a target sequence and leaves no overhang. Examples: Eco RI, Hin d II, etc.