Extinct Bird Enables Scientists to Propose the Half-Life of DNA

The giant Moa, an extinct type of flightless bird that once roamed the forests and plains of New Zealand is helping scientists to calculate the half-life of DNA.  A team of international researchers have analysed the fossilised bones of three species of these ancient birds and this study suggests that the DNA double helix can persist in the fossil record for a lot longer than previously thought.

The research, which has been challenged by a number of leading academics and geneticists proposes that under optimum conditions, genetic material relating to organisms can survive in the fossil record for a lot longer than previously thought.  Based on the calculations presented by this team, traces of genetic material might still be detectable in fossils that are around 6.8 million years old.

What is DNA?

DNA (Deoxyribonucleic acid) is a complex molecule that encodes the genetic information used in the development, maintenance and functioning of virtually all known living organisms*.  The DNA is located in the chromosomes, these in turn, are found in the nucleus of most cells.

* Many types of viruses, microscopic biological agents that reproduce inside the cells of living hosts do not have DNA.  Instead, these viruses contain a closely related complex molecule called RNA (ribonucleic acid).  It is the RNA that contains the genetic material.  RNA and DNA are different in a number of subtle ways.  For example, RNA is formed by a single strand, whilst DNA is shaped as a double helix.

Why is this Study Controversial?

This study suggests that fragments of genetic material could persist for many millions of years longer than previously thought.  Up until very recently, scientists thought that it was virtually impossible for any delicate, organic structures like the phosphates, sugars and proteins that make up DNA to survive for anything more than a few tens of thousands of years.  Once an organism dies, the body decomposes and is broken down by other organisms and physical/chemical processes.  Minute portions of DNA have been recovered from the frozen flesh of Woolly Mammoths (M. primigenius), but the double helix representing the DNA has been degraded into extremely short fragments.

Previously DNA Fragments Recovered from Ice Age Mammals Less than 100,000 Years Old

Fragments of DNA recovered from cells within the frozen corpse of a Woolly Mammoth.

Fragments of DNA recovered from cells within the frozen corpse of a Woolly Mammoth.

Picture Credit: Everything Dinosaur

What is the Half-Life of DNA?

The term half-life refers to a measurement that records the time elapsed for a substance to fall to half its measured value.  This term is commonly used in physics and chemistry in the measurement of radioactive decay. The scientist in the Moa study have calculated the half-life of DNA, if this measuring technique is validated by other researchers repeating the experiments and achieving the same results, then the dating of fossils could become much easier and the search for viable genetic material in fossils intensified.

To read a more complete article on this research: Controversial Research Leads to a Re-Think over DNA Preserved in Fossils

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