The structure and function of DNA are highly interrelated. From the composition of base pairs to their spacial arrangement understanding the structure and function of DNA as the molecule of inheritance is of paramount importance to grasp modern genetics.
Most living organisms carry and pass on their genetic information through a biological macromolecule known as deoxyribonucleic acid or DNA (some viruses are the exception, they use RNA). Basically, DNA is made of nucleotide bases with some sugars and phosphate molecules. In order to understand modern genetics a person must understand the structure and function of DNA as the molecule of inheritance.
What is the Structure for DNA?
DNA is a big and long polymer made of subunits called nucleotide monomers. Each nucleotide monomer is made of a nitrogenous base, a 5-carbon sugar (ribose or deoxyribose), and a phosphate group. In DNA, there are four nucleotide bases: cytosine (C), adenine (A), guanine (G), and thymine (T). Adenine and guanine are purines (chemically, a pyrimidine ring fused to an imidazole ring), while thymine and cytosine are pyrimidines (a heterocyclic aromatic organic compound similar to benzene and pyridine). When the four nucleotides are mixed together they are able to interact in a very specific way according to their chemical structure: adenine with thymine and cytosine with guanine.
The DNA molecule is made of two strands of nucleotide polymer chains coiled together into a double-helix pattern. The double helix is stabilized by the hydrogen bonds that form between the nucleotide bases, as determined by their chemical affinity: adenine with thymine and cytosine with guanine. This gives the molecule a great stability. The DNA molecule is able to be further folded and compacted many times to form chromosomes which are located inside the cell’s nucleus.
The Structure and Function of DNA as the Molecule of Inheritance
The DNA’s function is to serve as the reservoir of all the genetic information of the organism. This molecule contains genes, and one definition is that they are stretches (pieces) of the DNA molecule that code for specific functions. Crudely speaking, each gene will code for a specific protein that will carry out a specific function in the complex web of the cell’s biochemical metabolism. Everything that the organism has to do or make is specified in this DNA macromolecule: when a cell will develop, which type of cell will develop, when to live or die is all specified in the genetic material (DNA).
In addition, the DNA molecule functions as the instrument to pass on information from one generation to the other. When the cell has to duplicate, the DNA helix splits apart and each strand serves as a template to make a complementary strand of itself. This way all the information stored in the parent’s DNA is passed on to its offspring.
In humans the genes are contained in 46 chromosomes - you inherit one pair (23 chromosomes) from your father and one pair from your mother.
-Voet & Voet. (2007). Biochemistry. J. Wiley & Sons ISBN : 047158651X
-Sinden R. R. 1994. DNA structure and function.Gulf Professional Publishing, Second edition. ISBN 0126457506
Picture: courtesy of svilen001 -free pics at www.sxc.hu