chromosome of 150,000,000 nucleotide pairs, containing about 3000 genes 
Figure 11. The organization of genes on a typical vertebrate chromosome. Proteins 
that bind to the DNA in regulatory regions determine whether a gene is transcribed; 
although often located on the 5' side of a gene, as shown here, regulatory regions can 
also be located in introns, in exons, or on the 3' side of a gene. The intron sequences 
are removed from the primary RNA transcripts that encode protein molecules to 
produce a messenger RNA (mRNA ) molecule. The figure given here for the number of 
genes per chromosome is only a minimal estimate. 
From Alberts, B., Bray, D., Lewis, J., Raff, M., Roberts, K., and Watson, J. D. 1989. 
Molecular Biology of the Cell, 2nd edition. New York: Garland, p. 487. 
