Ene Cloning (the construction of a cDNA library…)

The Essay Question is below (Please Note, that this essay question is Divided into two parts and each count 50% (50 marks for each).

Describe in detail the construction of a cDNA library from an extract of human brain cells.(50 marks)

Outline three possible ways which may be used to screen this library for a gene whose protein product has been previously isolated. (50 marks)