This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Among the biochemical methods of genetic engineering, the Western Blot detects: 
Select and explain. 
A. mRNA, B. DNA, C. RNA, D. Protein
D: Protein
Answer: D: Protein 
Explanation: Southern blotting is used to identify and isolate a specific DNA sequence and can also quantitatively determine the number of times a specific sequence occurs in a paicular cell type. Western blotting is a biochemical technique, adapted from a similar technique for DNA of Southern blotting, for detection and identification of specific proteins. Nohern blotting allows researchers to determine the level of production (and, therefore, control of expression) of a paicular mRNA by quantitative determination of the relative amount of that paicular mRNA relative to total mRNA. A method was also developed to detect post-translational modifications to proteins (eastern blotting). Ref: Weil P. (2011). Chapter 39. Molecular Genetics, Recombinant DNA, & Genomic Technology. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.