Category Archives: Dr James Sleigh

Komodo, the Magic Dragon

by Dr James Sleigh

To celebrate the appearance of PlayDNA on the BBC’s Dragons’ Den, we are diving into the mystical world of dragons…

Here be dragons

Here be dragons

Powerful, fearsome, venomous. A rare breed of predator with sharp claws, razor-like teeth, and an insatiable appetite. No, we are not talking about Deborah Meaden, Peter Jones, or even Duncan Bannatyne of Dragons’ Den fame. We are describing the Komodo dragon, the largest living lizard, and native of the Indonesian Islands of Southeast Asia. But, do they deserve their dragon moniker?

They have no wings, and they can’t breathe fire, you say. Nor do they live for centuries, or like to hoard gold.

A real dragon

A real dragon
Photo courtesy of

Not a real dragon

Not a real dragon
Photo courtesy of

Nevertheless, these creatures, which can grow to over three metres in length and eat up to 80% of their body weight in a single feed, do possess an almost mythical ability worthy of the dragon name.

0117_MALO_Komodo_Eggs_013A_t607Miraculously, in separate zoos in the UK (Chester and London), two female Komodos, which were completely isolated from males, laid clutches of eggs that resulted in lots of baby dragons. This ability for females to produce offspring without mating with a male is known as parthenogenesis, and is very rarely seen in vertebrate species (those with a backbone like you and me). In fact, only about 1 in 1,000 vertebrates can reproduce in this manner. It was particularly unexpected that such a large animal as the Komodo dragon would join this rather selective group.

Intriguingly, all the virgin baby dragons were males. This is because of the interesting genetics of Komodos. Much like we have X and Y sex chromosomes (XX = female and XY = male), Komodo dragons have W and Z chromosomes. However, rather than females having two of the same sex chromosome like humans, female Komodos have one W and one Z chromosome while males are ZZ. When female dragons are isolated from males, through parthenogenesis they are able to duplicate either their W or Z chromosome (along with the rest of their non-sex chromosomes), resulting in eggs that are either WW or ZZ. The WW eggs do not survive, but the ZZ eggs produce viable male baby dragons.


Hello mummy!
Photo courtesy of BBC

It is believed that this ability to switch between sexual and asexual reproduction has evolved as a strategy to be able to survive in the Komodo’s natural habitat of isolated islands. Females finding themselves washed up on unpopulated islands are able to reproduce asexually, producing males for future mating.


Not quite cloning, but I’m sure some of the BBC dragons would be interested in making similar duplicates of themselves so they could make twice as much money! What’s that? You want to know the outcome of PlayDNA’s adventure in the dragon’s lair? Well, you will just have to wait until Sunday to see how Dr. Sam and Dr. Stuart fared…

PlayDNA is on Dragons Den Sunday 2nd February BBC2 at 9pm.

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Happiness is in the genes of the beholder

It’s a grey miserable Friday the 13th, so what better time to think about happiness! james2 copy

The always cheerful (no matter what the weather!) Dr James Sleigh explains how recent research suggests that happiness and health are actually linked on a biological level…

How often do you feel happy?

How often do you feel that you have contributed something to society? How often do you feel that you belong to a community group?

CharlotteWell, the answers to those questions now appear to affect more than just your mental and social well-being. New research suggests that your level of long-term happiness and self-satisfaction also has a significant effect on your genes.

A team of scientists in the US decided to study how positive psychology impacts gene expression levels in humans.

centraldogma copyGenes are short sections of your DNA that are copied to produce intermediate molecules called RNA, which can then be used as templates to create proteins, the fundamental components of all cells. When we talk about gene expression levels, we are describing how many intermediate ‘RNA’ copies are made from a particular gene.

When a gene or sets of genes are expressed at different levels to what is expected or normally observed in a particular group of people, this can sometimes indicate that something is perhaps not quite right.

Jo and familyv1In the study, the researchers took blood samples from 80 healthy people and looked at the expression of all the genes in the human body.

They also asked the volunteers a range of questions about their psychological well-being in order to determine whether their happiness was more due to having a deep sense of purpose in life, or perhaps more due to instant self-gratification, for example through going on regular holidays or getting to eat your favourite food.

sam and stuThe study found that those people who believed that they had a greater meaning in life had low expression of genes involved in unwanted inflammation and high expression of genes linked to a healthy immune system.

The opposite was true of the group of people whose happiness was mainly a product of immediate self-satisfaction.

These differences can have a major impact on general health because having high expression of inflammatory genes is linked to cardiovascular and other diseases, while having low expression of immune system genes can affect your ability to fight off infection.

Kel and Scotty

Interestingly, both groups had similar positive feelings about their lives, indicating that the subtle differences in happiness have a greater effect on the genome, and therefore your health, than they do on the conscious adult mind.

So the moral of the story is that doing good by others and trying to live a meaningful life is perhaps better for your long-term health than making yourself feel happy in the short term.

Reference: A functional genomic perspective on human well-being (2013) PNAS

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A genome’s junk is a gene’s treasure

Research Profile Picture James Sleigh

By James Sleigh


2012 was an eventful year.

We saw Queen Elizabeth II mark 60 years on the British throne, Team GB excel at the fantastic London Olympic and Paralympic Games, the re-election of US and Russian presidents, and Gangnam Style conquer the world, all while managing to survive the Mayan apocalypse.

The year will also be remembered for a number of considerable scientific achievements. But which is the most important?

The landing of the Curiosity Rover on the surface of Mars? The discovery of the Higgs boson at CERN? Or perhaps even Herr Baumgartner’s record-breaking skydive from 24 miles above the New Mexico desert?

Deciding is almost as tricky as picking last year’s BBC Sports Personality of the Year!

As the newest member of the PlayDNA team, I’ve decided to begin the year by highlighting the research from 2012 that I think has the greatest impact on our understanding of what makes us human.

The Human Dictionary

Spot the difference?

Spot the difference

You may think you’re quite different from a grasshopper, the mould growing on your week-old loaf, or your Mum’s cheese plant. And you would be quite right. But, despite the instructions to create each species being different, the pen with which they are written is the same.

That is, we all share a universal genetic code – the DNA (the instructions) of all organisms is made from long strings of consecutive molecules known as nucleotides, which come in one of four different flavours (A, C, T, or G). The order in which these nucleotides are arranged within DNA affects how the inherent information is read, and what creature is eventually produced.

This happens because relatively short, distinct stretches of DNA known as genes, are copied to produce intermediary molecules that are then used as a templates to create proteins, the fundamental components of all cells.

Original cartoon by Daniel Paz

Original cartoon by Daniel Paz

Thanks to the Human Genome Project (HGP), the entire instruction manual to build a human was mapped and published in 2003. This landmark scientific collaboration unravelled the sequence of all the letters in our DNA, and identified that each of us possesses a unique complement of about 3 billion nucleotides, including some 20,000 or so genes.


However, the term “genome” is perhaps somewhat of a misnomer, as unexpectedly genes were shown to account for only approximately 1% of the total DNA. The remaining 99% has since often been described as “junk” because it had not been linked to any particular function.

That is, until now.

The Human Encyclopaedia

ENCODE nature cover 1Picking up where the HGP left off, the Encyclopaedia of DNA Elements (ENCODE) project is a decade-long study, involving over 440 scientists in 32 laboratories, and costing in excess of £180 million. The primary results from this large international collaboration were published late last year across 30 scientific papers, and have earned the ENCODE project my pick for the breakthrough of 2012.

The main aim of the ENCODE project is to build upon the human lexicon described by the HGP, by improving our knowledge of the grammar that weaves the directory of words into meaningful sentences. That is, the ENCODE project is attempting to better our understanding of how our genome of 3 billion nucleotides fits together, how the genes are controlled, and what all that “junk” is actually for.

dnaUsing nearly 150 different cell types, the scientists studied on a very large scale many different properties of human DNA sequences. They looked at which regions were active, which were silent, and what sequences appeared to be important for driving the production of proteins.

Each type of cell uses different combinations and permutations of these DNA sequences to produce its own unique biology. By comparing these differences, we are able to better understand how the genome is put together, processed, and read.

The upshot from what is the most detailed analysis of the human genome to date is that approximately 80% of our DNA has now been assigned a biochemical function.

junk dna

Image credit:

It’s not junk!

Why should I care about that?!

Well, understanding what all the regions of the human genome are doing can help scientists to pinpoint certain genetic risk factors that predispose to different conditions. In the past, many studies looking at patient DNA sequences have found hotspots that appear to contribute in some way to particular diseases. Intriguingly, many of these regions were not found in genes but in the “junk,” making it hard to deduce how and why these seemingly unimportant parts of the genome were being correlated with certain diseases.

In light of the ENCODE results, it is highly likely that these regions are functionally impacting genes that at first glance did not appear to be involved in disease.

Just what the doctor ordered?

Just what the doctor ordered?

We are a long way from understanding the wealth of data that ENCODE has produced. And it’s not going to get any easier, as it is estimated that the project is only about 10% complete.

Nevertheless, by highlighting the importance of our genome’s “junk” for the function of our genes, this breakthrough project will undoubtedly lead to a deeper knowledge of diseases and how to treat them.

Dr James Sleigh is a published research scientist at the University of Oxford currently working on diseases that affect the nervous system. His interest in genetics and neuroscience was sparked while working in a lab at Harvard Medical School as an undergraduate, and he has never looked back! James is passionate about communicating science, and has even won awards for his science writing. He is the research correspondent for the SMA charity The Jennifer Trust and has recently joined PlayDNA as Chief Communications Officer – so no doubt you will be hearing plenty more from him!

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Filed under Author, Dr James Sleigh, Genetics, Science