The 5th DNA base

Hello learner,

I hope you are doing well.

In today’s newsletter, I will discuss the 5th DNA base! And its mysterious presence in our genome.

DNA is a type of nucleic acid made up of sugar, phosphate and nitrogenous bases. Adenine, cytosine, guanine and thymine are four different nitrogenous bases that make the double-helical DNA structure through hydrogen bonds.

Due to the presence of this nitrogenous base, individual nucleotide monomers (sugar + phosphate + base) are known as nucleotide A, nucleotide C, etc.

Now, here is where the magic happens!

This unique combination of three different nucleotides (the triplet codon) synthesizes an amino acid and the long amino acid chain. After completing the folding process, this will finally prepare a protein.

This is a common and routine cellular activity for all the organisms on Earth— four different bases, triplet combination, amino acid chain and a protein. You can now understand how these bases play an important role in this whole process.

Scientists identified a fifth DNA base, which, when present in the DNA, influences the whole process of gene expression.

You heard it right!

5-methylcytosine is a methylated version of the cytosine base. It behaves differently than cytosine; that’s why it is considered the fifth base. Interestingly, when it presents in the sequence, it turns off gene expression!

What does that mean?

It actually disallows a gene to synthesize a protein.

This process is known as DNA methylation— the addition of a methyl group on a DNA base, particularly on a cytosine base. It’s a chemical modification and not a sequence-level modification.

This means that the sequence will look the same, but the chemical structure has one additional methyl group. At a molecular level, this chemical modification prevents enzymes from working efficiently for transcription and disallows a gene to undergo the transcription process.

Consequently, a protein’s sufficient copies can’t be prepared and results in abnormality.

So, DNA methylation is like a lock on a gene! Nature has locked so many genes and DNA sequences from our genome using DNA methylation.

This is a part of nature’s regulatory system; when genes aren’t needed, nature locks it, permanently by the fifth base. Scientifically speaking, this will give an evolutionary benefit to the organism to better adapt to existing conditions.

However, dysregulation in this system causes abnormal gene expression. Our bad habits and environment cause hypermethylation and hypomethylation and result in the underexpression or overexpression of a gene, respectively.

Let me simplify it!

This means that when a gene is required in a higher amount, it under-expresses, while when it isn’t required much, it over-expresses and results in a catastrophe known as “cancer.”

Our responsibility is to protect the locked areas and prevent the active genes from being locked.

That’s it!

And we are failing to do this simple task. Cancer is the most common cause of death worldwide nowadays; that’s the proof!

However, on our own, we can’t do much, as it is a global situation now. Our air, water and natural resources are already polluted and resulting in epigenetic dysregulation.

So, in conclusion, the fifth base is both beneficial and harmful to us.

Such research helps us to understand how complex our genome is and how tightly the whole synthesis is regulated and controlled by nature.

And we are still questioning the existence of nature!

I hope you enjoyed the reading!

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Cheers,

Dr Tushar

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