'Junk' DNA inherited from our ancient ancestors may rewire our brains

‘Junk’ DNA inherited from our ancient ancestors could be rewiring our brains and altering our behaviour and emotions, study finds

  • Half of the human genome is so-called ‘junk’ DNA that doesn’t code for proteins
  • Much of this comes as ‘transposons’ which change position between people
  • Researchers from Oxford examined the expression of transposons in fruit flies
  • They found that they are associated with genes that control brain activities
  • These include functions like the formation of memories and the sleep-wake cycle

Some of our brain’s activity could be being guided by so-called ‘junk DNA’ we inherited from our ancient ancestors, a new study has concluded.

The human genome contains all the instructions needed to build and maintain our bodies — however half of it appears to be ‘junk’ that doesn’t code for any proteins.

Much of this mysterious extra DNA comes in the form of transposons — or ‘jumping genes’ — which can move around between people and appear in different places.

It is thought that transposons originated from ancient viruses — and can today be harmful if they have ‘jumped’ into a gene such as to disrupt cellular processes.

However, recently experts have proposed that this ‘junk’ information may in fact play an active and beneficial role in our bodies. 

Working with flies, expert from the University of Oxford have found that transposons appear to be related to specific genes that control our behaviour and emotions.

Some of our brain’s activity could be being guided by so-called ‘junk DNA’ we inherited from our ancient ancestors, a new study has concluded

At Oxford’s Centre for Neural Circuits and Behaviour, researchers have been investigating transposon activity in unprecedented detail in the brains of fruit flies — which are used a model organism — by means of so-called single-cell sequencing.

Their findings showed that transposons are not active across the whole fly brain, but instead operate in certain areas only, forming distinct patterns of expression.

Moreover, these patterns appeared to be linked to genes located near transposons — suggesting that this ‘junk’ DNA may in fact play a beneficial role in our bodies. 

To investigate further, molecular biologist Christoph Treiber and colleagues used software tools they developed to explore how transposons are expressed.

They found that transposons segments are often part of the messenger RNA sent from neural genes in the cell nucleus out to the cytoplasm where proteins are made.

This suggests that transposons may be used to alter neural function — and act on genes that have roles in such brain activities as the formation of memories and the sleep-wake cycle.

‘We know that animal genomes are selfish and changes that are not beneficial often don’t prevail,’ said Dr Treiber.

‘Since transposons are parts of hundreds of genes in every fly strain that we looked at, we think these physical links likely represent an advantage for the fly.’

‘We now want to understand the impact of these new alleles on the behaviour of individual animals.’

‘Transposons might broaden the range of neuronal function in a fly population, which in turn could enable a few individuals to react more creatively in challenging situations,’ he added.

‘Also, our preliminary analyses show that transposons might play a similar role in our brain,’ said Dr Treiber.

‘Since every person has a unique transposon “fingerprint”, our findings could be relevant to the need to personalise pharmacological treatments for patients with neurological conditions.’

The full findings of the study were published in the journal Genome Research.

DNA AND RNA EXPLAINED: THE MOLECULES THAT CONTAIN THE GENETIC INFORMATION FOR LIFE

DNA – deoxyribonucleic acid – is widely known as the molecule found in the nucleus of all our cells that contains genetic information.

It is shaped like a double-helix and made of small sections called nucleotides. 

Each nucleotide contains a nucleobase, a sugar, and a phosphate group.

The sugar component in this particular molecule is called deoxyribose and makes up the D in DNA.

This is a cyclic carbon-based chemical with five carbon atoms arranged as a pentagon.

At the second carbon atom there is an attached singular hydrogen atom in deoxyribose.

This can also have an additional oxygen attached as well. 

In this case, the oxygenated chemical then forms what is simply known as ribose – the R in RNA. 

The deoxy prefix literally means without oxygen.

Shape of RNA and DNA

RIbose can do almost everything deoxyribose can and also codes for genetic information in some cells and organisms.  

When the oxygen is present it drastically alters how the chemicals bonds and sits alongside other molecules. 

When oxygen is present – in RNA – it can take a variety of shapes. 

When oxygen is not present in this specific location – in DNA – the molecule forms as the iconic double helix. 

Uses of RNA 

DNA is often broken down into RNA and read by the cells in order to translate and transcribe the genetic code in order to make proteins and other molecules essential for life. 

RNA uses three of the same base pairs as DNA: Cytosine, Guanine, Adenine.

The othe base pair, Thymine, is swapped out in RNA for Uracil. 

RNA is also often found in simpler organisms, such as bacteria. 

It is often also a virus, with Hepatitis, flu and HIV all forms of RNA. 

Mitochondrial RNA 

All animal cells use DNA, with one notable exception: the mitochondria.

Mitochondrian are the powerhouses of the cell and turn glucose into pyruvate and then into Adenosine triphosphate (ATP) via the Krebs cycle. 

This process is all done in this one organelle in the cells and ATP is the universal form of energy and used throughout every aerobic organism. 

In the mitochondria there is a small strand of RNA which is unique in the animal kingdom. 

It is passed down from the mother exclusively (the father’s lives in the sperm but is dissolved during fertilisation) and allows humans to trace their maternal lineage back throughout time.  

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