Neanderthal DNA and Modern Humans: Svante Pääbo Receives the 2022 Nobel Prize in Physiology or Medicine

What makes humans “human”?

Neanderthal DNA sequencing from ancient bone samples

On October 3, 2022, the Nobel Assembly at Karolinska Institutet announced the 2022 Nobel Prize in Physiology or Medicine had been awarded to Svante Pääbo, director of the Department of Genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. The Assembly cited his “discoveries concerning the genomes of extinct hominins and human evolution”. They mentioned the highlight of his research: the seemingly impossible task, at the time, of sequencing the Neanderthal genome. The discoveries that followed from this sequencing project continue to redefine our understanding of modern human origins.

The award showcases the technological advancements made in the analysis of ancient DNA. However, Pääbo’s research had an inauspicious beginning. In 1985, he published the results of his early work, cloning and sequencing DNA fragments from a 2,400-year-old Egyptian mummy (1). Unfortunately, later analysis revealed that the samples could have been contaminated by the researchers’ own DNA (2).

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High-Molecular Weight DNA for Long-Read Sequencing

Imagine that you’re putting together a large, complex jigsaw puzzle, comprising thousands of exceptionally small pieces. You lay them all out and attempt to make sense of them. It would be far easier to assemble this puzzle were the pieces larger, containing more of the image advertised on the box. The same can be said when sequencing a genome.

high-molecular weight DNA  Depiction of a DNA helix

Traditional short-read or next-generation sequencing relies on DNA spliced into small fragments (≤300 base pairs) and then amplified. While useful for detecting small genetic variants like single-base changes to the DNA, this type of sequencing can fail to illuminate larger variations (typically over 50 base pairs) in the genome. Long-read sequencing, or third generation sequencing, allows more accurate genome assemblies, facilitating better detection of structural variants like copy number variations, duplications, translocations and inversions that are too large to identify with short-read sequencing. Long-read sequencing has the capability to fill in “dark regions” of a genome that are unfinished and can be used to assemble larger, more complex genomes using longer fragments of DNA, or high-molecular weight (HMW) DNA.

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ProDye Brings Sanger Sequencing to Multiple Platforms

Researchers looking for new chemistry for Sanger sequencing need look no further than the ProDye™ Terminator Sequencing System, developed by Promega for use in capillary electrophoresis instruments. Sanger sequencing, or dye-terminator sequencing, has been the gold standard of DNA analysis for over 40 years and is a method commonly used in labs around the world. Even as new technologies emerge, Sanger sequencing remains the most cost-effective method for sequencing shorter pieces of DNA.

Sanger sequencing depicted as results on a musical cleft
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Harnessing the Power of Massively Parallel Sequencing in Forensic Analysis

The rapid advancement of next-generation sequencing technology, also known as massively parallel sequencing (MPS), has revolutionized many areas of applied research. One such area, the analysis of mitochondrial DNA (mtDNA) in forensic applications, has traditionally used another method—Sanger sequencing followed by capillary electrophoresis (CE).

Although MPS can provide a wealth of information, its initial adoption in forensic workflows continues to be slow. However, the barriers to adoption of the technology have been lowered in recent years, as exemplified by the number of abstracts discussing the use of MPS presented at the 29th International Symposium for Human Identification (ISHI 29), held in September 2018. Compared to Sanger sequencing, MPS can provide more data on minute variations in the human genome, particularly for the analysis of mtDNA and single-nucleotide polymorphisms (SNPs). It is especially powerful for analyzing mixture samples or those where the DNA is highly degraded, such as in human remains. 

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Remembering Frederick Sanger and Sanger Sequencing

It is with sadness that we recognize the passing of Dr. Frederick Sanger. Sanger is known to molecular biologists and biochemists worldwide for his DNA sequencing technique, which won for him the 1980 Nobel prize in Chemistry.

Also noteworthy, Sanger’s laboratory accomplished the first complete genome sequence, that of a viral DNA genome more than 5,000 base pairs in length.

The 1980 prize was Sanger’s second Nobel award, his first awarded in 1958 for determining the chemical structure of proteins. In this work, Sanger elucidated not only the amino acids that comprised insulin but also the order in which the amino acids occurred.

About Sanger Sequencing
Sanger DNA sequencing is also known as the chain-termination method of sequencing. The Sanger technique uses dideoxynucleotides or ddNTPs in addition to typical deoxynucleotides (dNTPs) in the reaction. ddNTPs result in termination of the DNA strand because ddNTPs lack the 3’-OH group required for phosphodiester bond formation between nucleotides. Without this bond, the chain of nucleotides being formed is terminated.

Sanger sequencing requires a single-stranded DNA, a DNA primer (either radiolabeled or with a fluorescent tag), DNA polymerase, dNTPs and ddNTPs. Four reactions are set up, one for each nucleotide, G, A, T and C. In each reaction all four dNTPs are included, but only one ddNTP (ddATP, ddCTP, ddGTP or ddTTP) is added. The sequencing reactions are performed and the products denatured and separated by size using polyacrylamide gel electrophoresis.

Diagram of Sanger dideoxy sequencing. (Courtesy  of Wikipedia and Estevez, J.)
Diagram of Sanger dideoxy sequencing. (Courtesy of Wikipedia and Estevez, J.)

This reaction mix results in various lengths of fragments representing, for instance, the location of each A nucleotide in the sequence, because while there is more dATP than ddATP in the reaction, there is enough ddATP that each ATP ultimately instead is replaced with a ddATP, resulting in chain termination. Separation by gel electrophoresis reveals the size of these ddATP-containing fragments, and thus the locations of all A nucleotide in the sequence. Similar information is provided for GTP, CTP and TTP.

The Maxam and Gilbert DNA sequencing method had the advantage at the time of being used with double-stranded DNA. However, this method required DNA strand separation or fractionation of the restriction enzyme fragments, resulting in a somewhat more time-consuming technique, compared to the 1977 method published by Sanger et al.

Dr. Sanger was born in Gloucestershire, U.K. in 1918, the son of a physician. Though he initially planned to follow his father into medicine, biochemistry became his life-long passion and area of research endeavor. Sanger retired at age 65, to spend more time at hobbies of gardening and boating.


Sanger, F. , Nicklen, S. and Coulson, A.R. (1977) DNA sequencing with chain-terminating inhibitors. Proc. Natl. Acad. Sci. USA 74, 5463-7.

Maxam, A.M. and Gilbert, W. (1977) A New Method for Sequencing DNA. Proc. Natl. Acad. Sci. USA

There is something special about seeing the original Sanger publication from 1977, available here as a scan.

Dietary Analysis, DNA Style

dna testing of foodDNA testing methods are being used to solve problems in an ever-increasing number of fields. From crime scene analysis to tissue typing, from mammoths to Neanderthals, and from Thutmose I to Richard III, both modern mysteries and age-old secrets are being revealed. The availability of fast, accurate, and convenient DNA amplification and sequencing methods has made DNA analysis a viable option for many types of investigation. Now it is even being applied to solve such mundane mysteries as the precise ingredients used in a sausage recipe, and to answer that most difficult of questions “what exactly is in a doner kebab?” Continue reading “Dietary Analysis, DNA Style”

Sonnets in DNA

William ShakespeareFor sixty years now, scientists have studied the role of DNA as a vehicle for the storage and transmission of genetic information from generation to generation. We have marveled at the capacity of DNA to store all the information required to describe a human being using only a 4-letter code, and to pack that information into a space the size of the nucleus of a single cell. A letter published last week in Nature exploits this phenomenal storage capacity of DNA to archive a quite different kind of information. Forget CDs, hard drives and chips, the sum of human knowledge can now be stored in synthetic DNA strands. The Nature letter, authored by scientists from the European Bioinformatics Institute in Cambridge, UK, and Agilent Technologies in California, describes a proof-of-concept experiment where synthetic DNA was used to encode Shakespeare’s Sonnets, Martin Luther King’s “I Have a Dream” speech, a picture of the Bioinformatics Institute, and the original Crick and Watson paper on the double-helical nature of DNA. Continue reading “Sonnets in DNA”