(a) Carrier 

An individual who possesses an unexpressed, recessive trait. 

(b) cDNA library 

A collection of DNA sequences that code for genes. The sequences are generated in the laboratory from mRNA sequences. 

(c) Clone 

An exact copy made of biological material such as a DNA segment (eg. a gene or other region), a whole cell, or complete organism. 

(d) Cloning 

Using specialized DNA technology to produce multiple, exact copies of a single gene or other segment of DNA to obtain enough material for further study. Process, used by researchers in the Human Genome Project, referred to as cloning DNA. Resulting cloned (copied) collections of DNA molecules constitute clone libraries. Second type of cloning exploits the natural process of cell division to make many copies of an entire cell. The genetic makeup of these cloned cells, called cell line, is identical to the original cell. Third type of cloning produces complete, genetically identical animals such as the famous Scottish sheep, Dolly.