Contact: to feature here

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Ancient DNA could tell a lot of different stories
Information or “recipe” for every living organism is contained in DNA material (or RNA, in some viral species). DNA is composed of nucleotides aligned in two chains that bond together through complementary base pairing. Result is typical double helix shaped molecule. Every living creature should be proud of his uniqueness - there aren’t two individuals (except identical twins) that have the same DNA. Thanks to that fact, molecular fingerprinting is used for identification of the single individual, forensics can identify suspects, and paternity test could be performed … Growing number of experiments use DNA for gathering different kind of information. Since DNA material is able to survive long period of times, excavation of the various plant or animal remains could tell us a lot of different stories about past on the Earth.

Ancient DNA represents DNA material extracted from old biological samples. Unlike classical DNA analysis, these specimens are of less quality. Archeological discoveries of different animal and plant materials precede DNA analysis. Even though DNA is present in each cell of the living organism, decomposition of the body after death limits the sources that could provide sufficient DNA for the further analysis. In the rare situations when body is entrapped in the ice or amber, high quality and quantity DNA is available. Various insects, plants and bacterial species were successfully investigated after DNA was extracted from amber entrapped specimens. For animal species, usual source of DNA are bones and teeth. Weather conditions (especially temperature and moisture) greatly affect the speed of DNA decay. At temperature of -5 Celsius, mitochondrial DNA is degraded to 1 base pair after 6.830.000 years. Degradation of the nuclear DNA is two times faster than mitochondrial. Using PCR method, scientists were able to multiply and investigate some very old samples dating back from Cretaceous period (145-66 million years ago). Not all ancient DNA samples are million years old. Some ancient DNA analysis investigates remains of much younger origin.

One recently published article investigates climate changes based on analysis of the ancient urine. Rock hyrax is cute little creature that looks like a rodent but is actually more closely related to the elephant. They inhabit rocky environment in Sub-Saharan Africa and Middle East. These social animals have specially designated area serving as mutual (communal) toilets. They are used for years, containing urine samples of a lot of hyrax generations. Urine crystallizes in time, forming stratified accumulations known as middens. Scientists found well preserved 10 thousands year old African middens that could provide more insight in climate changes associated with the hyrax habitat. Collected samples were investigated for organic molecules, metabolites and plant derived molecules. Forensic DNA analysis provided more information on the type of diet they have in the past revealing what plants were available 30.000 years ago. Since plant species are typical representatives of the each climate zone, list of available species on the hyrax menu precisely inform scientist which climate type existed 30.000 years ago. Middens were used for pollen analysis as well. That analysis increased the accuracy of predicted climate type. Given results showed that southern African climate underwent series of complex climate changes after last ice age (~20 000 years ago). Future experiments will investigate changes middens undergo when exposed to computerized simulations of past climate changes. Scientists are hoping that provided information would be helpful in revealing mysteries behind fast and unpredicted weather changes in this dynamic environment.

Another location and another set of animal excrements also provided evidence on previously lived flora and fauna. North West area of Australian continent is arid and any kind of old DNA is hard to find. However, scientists managed to found 700 - 30.000 years old samples of urine, fecal matter, hair, bones and eggshells cemented together in three locations. Different species (now extinct common brushtail possum and various arid grasses) that inhabited Western Australia were easily detected thanks to genetic analysis. Previous investigations focused on carbon dating, macrofossils and pollen identification; DNA analysis expanded previous data and helped in creating final image of the environment from the past.

Analyses of this kind are especially important for endangered species. Future conservation plans and efforts will work better if scientists become fully familiar with extinct species and be able to compare existing environmental data with the ones from the past.
Like Post Reply
The initial study of ancient DNA (aDNA) dates back to the year 1984 when a scientist named Russ Higuchi and his colleagues separately described DNA sequences from a type of zebra (quagga) and an ancient Egyptian individual that were 150 and 2400 year old specimens respectively. aDNA research is generally defined as the recovery of DNA sequences from museum specimens, archaeological discoveries, remains of the fossil and various unusual sources. The study of aDNA became possible with the invention of techniques that amplify specific DNA sequences with the aid of enzymes. At present the reports of analysed specimens that are hundreds, thousands, and also millions of years old are almost considered a routine.
The authenticity of ancient DNA (aDNA) is based on the following considerations:
• Examination of the associated remains that whether it is well preserved equally or do they show any evidence of contamination. Biochemical preservation of the specimen, which includes the preservation of other biomolecules that associate with the survival of the DNA, for instance, collagen or amino-acid racemisation (AAR), must indicate excellent sample preservation.
• Work areas must be isolated in order to separate samples and extracted DNA from PCR amplified products. Screening for the various contaminants that enter at any stage of the process is necessary and can be achieved by negative extraction control and amplification.
• The successful amplification of large fragments of the ancient DNA should be carried out with caution owing to DNA degradation.
• The reproducibility of the result is of utmost importance and should produce consistent results each and every time such as with polymerase chain reaction and extractions.
• Cloning of products is essential in order to access for contamination, damage and with jumping PCR (A method for reconstruction and replication of doubled stranded DNA that is randomly damaged, for instance, damaged DNA often found in mummified tissues or museum specimens).
• The results that are generated by carrying out the same experiment by various independent research groups should be consistent.
• Quantification is carried out by competitive PCR or Real-Time PCR to provide an indication of the initial number of templates in the reaction.
Like Post Reply
Handling ancient DNA is extremely challenging, from finding sufficient material to start with, until eliminating the contamination caused by various sources including modern human beings. Some damages to the DNA also cause changes in its sequence. Cytosine can convert to uracil, which is recognised by copying enzymes as thymine, which results in a C to T transition. Similarly changes from Guanine to Adenine also occur. Errors in the DNA molecule are very frequent at the ends.
During the early years, the study of genetic material from the ancient specimens was predominantly dedicated to investigate the DNA sequence of many extinct species, for instance Woolly Mammoth and Dodo. But during recent years the scientists are beginning to ponder on new question regarding ancient DNA revealing how the genetic constitution of prehistoric populations has changed through the time scale. And these findings will help scientists to unfold evolution.
Characterizing between the ancient genetic material and that of modern humans is particularly complicated when the aDNA comes from close relatives of modern human population. During the current years, ancient DNA has been utilized in the understanding of aspects biology of the Neanderthals. The sequencing of the mitochondrial (mtDNA) and nuclear DNA extracted from fossils have furnished information regarding the speech, appearance, capability and population structure of Neanderthals in addition to their phylogenetic relationship with the modern human beings.
Ancient DNA (aDNA) is also being utilized to shed light regarding the origin of modern humans. The analysis of available ancient DNA has provided the evidence that mitochondrial DNA (mtDNA) from Neanderthals looked reasonably different from the mitochondrial DNA (mtDNA) of early modern human beings. And this has supported to the theory that modern humans have a single African origin rather than the alternative theory of multiregional evolution, where the theory proposes that ancestors of modern humans and Neanderthals bred in the past.
Like Post Reply
Analysis of ancient DNA (aDNA) has various useful applications.

Ancient DNA analyses of the remains that are paleontological, historical and archaeological can contribute significant information for the conservation of species and populations that cannot be obtained any other means. The integration of ancient DNA into conservation genetics upholds a lot of potential, if employed sensibly. The analysis of ancient DNA also has the capability to make important and unique contributions to the areas of evolution and ecology.

Ancient DNA (DNA that is retrieved from things long dead such as fossil bones, museum specimens or mummies) techniques are extremely helpful in studies of conservation and evolutionary genetics. Cautious application of these techniques has enabled scientists to calculate approximately the levels and patterns of genetic variation thousands of years ago in a species, and how this variation has altered over time scale.

Researchers can also utilize ancient DNA analysis to reconstruct or rebuild the evolutionary relationships of endangered and extinct animals, allowing us to better characterize the species and populations and their evolutionary distinctiveness. For instance in the recent times, by utilizing these methods, researchers found that the five types of honeyeater species that once lived in Hawaii are not practically the same as Australasian honeyeaters, but were a separate family of Hawaiian birds. Convergent evolution had occurred because of similar foraging habits.

Ancient DNA techniques have also demonstrated that they are very valuable for studies regarding wildlife disease. They can allow us, for instance, to find out when native host populations were colonized by invasive pathogens, changes in the gene composition of the vectors and even to assess coevolution that can occur between host and parasite.

There are lots of applications of ancient DNA methods towards the issues in conservation and evolutionary biology. Some of the ongoing important research involves and endangered and extinct Hawaiian honeycreepers, quaggas, black-footed ferrets, ivory-billed woodpeckers, Indian wolves, forest robin etc to mention a few.
Like Post Reply

Users browsing this thread:
1 Guest(s)

Ancient DNA could tell a lot of different stories00