All life on Earth is based on building blocks, known as DNA (deoxyribonucleic acid), which exists in the form of a double helix. DNA is a highly elaborate and modular molecule with different levels of hierarchical complexity. In this post, we will examine some of the concepts about DNA. For those of you that are interested in fields such as astrobiology, transhumanism, and similar areas, it’s important to understand DNA as it has a direct bearing on much of the research being done in these emerging sciences today.
DNA is made up of nucleotides, which are themselves constructed from a molecule of sugar, a molecule of phosphate, and a base. The base is the most crucial part of the molecule as it is essentially the carrier of the genetic information, that when combined with other bases, codes your genetic makeup. Simply put, DNA is an amazing biological molecule, which essentially makes you… you.
As mentioned, DNA at its simplest level is made up of a combination of bases; Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). These bases exist in a chain on each strand of the double helix and join up in between the strands as complementary pairs of A-T and C-G. This sequence of base pairs is what codes for proteins to be made in your body, and thus is responsible for your appearance, your metabolism and thousands of other functions and features.
Sequences of bases that code for specific proteins to be produced are known as genes. They can be anywhere from only a few bases in length, to several million, with the average length in the human genome being approximately 3,000. For example, you can have a gene that determines eye color, or a gene that dictates the pigment of your skin. Different forms of a gene are known as alleles, so the gene for eye color has green, blue and brown alleles.
A DNA strand is made up of thousands upon thousands of genes, and also what is known as junk DNA. This junk DNA does not have a function, or rather, it does not have a function that is currently understood or known of in the scientific community. These DNA strands form a double helix, which is two strands of DNA joined at their complementary bases, in a spiral structure.
Chromosomes are tightly wound bundles of DNA strands, that look like two arms joint at the centromere, with the short arm designated “p”, and the long arm designated “q”. Two chromosomes join at the centromere to form a chromosome pair, which structurally resembles an “X”. The chromosomes are found in the nucleus of the cell, from where they replicate to form duplicates of themselves during cell division, or take part in the transcription/translation process whereby proteins are created from the genetic code.
DNA is complex
DNA, even when broken down into its constituent parts is incredibly complex and because of this, errors can easily creep into the code. Genetic disease and cancer typically come about due to these errors in the genome, and are exponentially copied during the copying and division of cells. So, DNA and its complexity are both a blessing and a curse but without it, life as we know it would not be possible.
Helpful DNA-related Resources:
- The National Human Genome Research Institute fact sheet Deoxyribonucleic Acid (DNA) provides an introduction to this molecule.
- Information about the genetic code and the structure of the DNA double helix is available from GeneEd.
- For additional information about the structure of DNA, please refer to the chapter called What Is AGenome? in the NCBI Science Primer. Scroll down to the heading “The Physical Structure of the Human Genome.”
- The New Genetics, a publication of the National Institute of General Medical Sciences, discusses the structure of DNA and how it was discovered.