Discovery Science: Earth – Evolution – Genetic information: DNA

Earth Science: Biology – Evolution – Genetic information: DNA

Genetic information is stored and passed on as deoxyribonucleic acid (DNA). The cells of all living organisms contain DNA, as do many viruses.

In eukaryotic cells, the chromosomes of the nucleus are made up of DNA. It is also found outside the nucleus in chloroplasts and mitochondria, and inside the cytoplasm in the form of plasmids. In prokaryotic cells, the DNA is always unbound within the cytoplasm. DNA molecules consist of nucleotides (polynucleotides) that are linked to each other in a chain.

Each nucleotide has three components: one sugar (deoxyribose), one phosphate, and one of the four bases adenine (A), cytosine (C), guanine (G), and thymine (T). All nucleotides contain the same sugar and phosphate backbone. The genetic information is, therefore, stored in the order of the bases. The famous model of the DNA double helix constructed by Watson and Crick in 1953 illustrates this structure.

Two twisted polynucleotide chains create a double helix held together by nucleotide base pairs. Periodical polyester chains between phosphates and the sugar backbone create the outer structure of the double helix. Between the strands, either adenine and thymine is paired by two hydrogen bonds, or cytosine and guanine are paired by three hydrogen bonds.

Adenine can only pair up with thymine and cytosine can only pair up with guanine (the principle of base pair complementarity). As a result, the base sequence along one polynucleotide strand determines the base sequence of the other strand. The strands of the double helix are therefore complementary, not identical, and oriented in opposite directions (antiparallel).

DNA needs not only to store genetic information, but also to identically reproduce this information in order to pass it on to the next generation. Replication of the information happens during interphase (the time period between two cell divisions). The complementary DNA strands break away from each other. An enzyme called DNA polymerase synthesizes a new strand by binding new complementary nucleotides to the now single bases.

Each of the original parent strands act as a template for the creation of a new complementary, antiparallel strand.


More than a thousand scientists have taken part in this international project, initiated in 1990, to determine the entire sequence of the human genome. In 1998, the American biologist Craig Venter founded Celera Genomics to map the genome through automated sequencing with the aid of private funds, thereby competing with the international protect.

In June 2000, both published their versions. Data analysis is ongoing, with the goal of early disease recognition and treatment.


In recent years, the so-called genetic fingerprint has received much attention. It offers a method of identifying criminals who can then be convicted on the basis of this evidence. This is made possible due to the fact that every person has a unique set of chromosomes.

Even the smallest trace left behind at a crime scene (for example, hair or body fluids) allows the re-construction of an individual DNA profile.