The chemical bonds that hold the two complementary strands of the dna double-helix close to one another are

The DNA double helix is comprised of several nucleotides. The nucleotides are adenine, guanine, cytosine and thymine. Adenine and guanine are purines. Cytosine and thymine are pyrimidines. The purines present on one strand form a hydrogen bond with the pyrimidines on the complementary strand. The adenine forms a pair with thymine and the cytosine forms a pair with guanine on the complementary strand. This hydrogen bonding between the several nucleotides result in the force that holds the two complementary strands together.

answer: 20 percent

the fish culture has become a developing commercial practice in developing countries which is already prominent in developed countries of the world. the major fish protein demand is being supplemented in developing countries is   fishing to meet the needs of the growing population. therefore, in some developing nations, the percentage of animal protein from fish in the diet can be as high as 20 percent.