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Modern Genetic Analysis Chapter 2. The Structure of Genes and Genomes
Solved Problem

2.

The human genome contains 3,000,000 kb and is estimated to contain 100,000 genes. If we make the simple assumption that the average size of the coding region of a gene (the part that codes for protein) is 2 kb, from these data

a. What can be concluded about the average spacing of the central point of genes on chromosomal DNA?
b. What can be concluded about the proportion of the genome that codes for protein?
c. What occupies the noncoding regions?
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Solution
a. The average spacing between the central points of genes must be 3,000,000 divided by 100,000, which equals 30 kb.
b. Since the protein-coding segment is only 2 kb, it is clear that only 1/15, or about 6 percent, of the genome actually codes for protein.
c. The remaining sequences must be composed of regulatory regions adjacent to genes, as well as repetitive DNA and nonrepetitive spacer DNA between the protein-coding regions and introns within the protein-coding regions.
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