Chapter 8, Problem 1CT

Summary Introduction

To describe:

The antiparallel arrangement of DNA.

Concept introduction:

Deoxyribonucleic acid (DNA) is a genetic material, which is responsible for passing of information from one generation to other. It is a double helical structure that consist two parallel strands made up of nucleotides.

Explanation of Solution

Nucleotides which consist of sugar, base and phosphate group are the subunits of DNA. One nucleotide subunit is linked to another nucleotide subunit by the phosphodiester bond between the sugar molecules of one nucleotide to the phosphate group of other nucleotide. DNA backbone is composed of phosphate group and deoxyribose sugar.

The purine bases pair with their complementary pyrimidines bases and form a nucleotide sequence. DNA is a double helical structure in which two strands of DNA are wound together as double helix in a chromosome.

The two strands of helical DNA are anti parallel to each other with nitrogenous bases stacked between the two strands giving it ladder like appearance. The strands of DNA helix are oriented in the opposite direction which is called antiparallel arrangement of DNA helix. One helix of DNA runs in the $\text{3'}\text{to}5\text{'}$ direction and other runs in $\text{5'}\text{to}\text{3'}$ direction. The antiparallel nature of double helix is important factor in DNA and protein synthesis.

Conclusion

The arrangement of two DNA strands in opposite direction contributes to the anti parallel nature of DNA double helix.