Student to attempt either option (A) or (B). (A) (i) Explain how is a bacterial cell made 'competent' to take up recombinant DNA from the medium.…

A bacterial cell is made competent by treating it with a specific concentration of a divalent cation such as calcium, which increases the efficiency with which DNA enters the cell through pores in its cell wall.

$\displaystyle \star$ Denaturation , DNA is heated to a high temperature resulting in the separation of two strands of DNA

$\displaystyle \star$ Annealing , two primers are annealed to each of the single-stranded template DNA.

$\displaystyle \star$ Extension , enzyme Taq polymerase extends the primers using the nucleotides provided in the reaction and the genomic DNA as template.

Transgenic animals : Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals.

Common reasons to produce transgenic animals are :

$\displaystyle \star$ Normal physiology and development, Transgenic animals can be specifically designed to allow the study of how genes are regulated and how they affect the normal functions of the body and its development.

$\displaystyle \star$ Study of disease, Many transgenic animals are specially made to serve as models for human diseases so that investigation of new treatments for diseases is made possible.

$\displaystyle \star$ Biological products , Transgenic animals that produce useful biological products can be created

$\displaystyle \star$ Vaccine safety , Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans.

$\displaystyle \star$ Chemical safety testing , Transgenic animals are made that carry genes which make them more sensitive to toxic substances than non-transgenic animals.