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February 08 2018


This Deep-Sea Creature Lays Its Eggs on Hydrothermal Vents—A First

The Pacific white skate lay its eggs on superheated hydrothermal vents, and then may wait more than four years for the eggs to hatch.

DNA Basics Chapter 3: DNA Expression

In the last post of the DNA Basics series we described the structure of DNA. To summarize briefly: DNA is the instruction manual to each of us.

Nucleotides are the letters;

Sets of three consecutive nucleotides called codons are the words;

Groups of codons called genes are the sentences; and,

Chromosomes are complete volumes of the 23-volume manual — one edition of which is inherited from each parent.

But who’s reading all of this? Who’s actually carrying out the instructions written there?

Heads up: This chapter does get down into the molecular nitty gritty a little bit, but if you bear with us, you’ll have a really solid foundation for understanding the way DNA products work, from ethnicity testing, to finding biological parents or children, and more.


Ribonucleic acid (RNA) is similar to DNA in many ways. It is also a molecule made up of 4 nucleotides — A, U, G, and C. A and U are complementary just like A and T are in DNA, and G and C are complementary like in DNA. RNA’s main function is to read DNA. Think of DNA as the original set of instructions written in ink, and RNA are the notes taken in pencil. RNA copies sections of DNA — a process called transcription, then turns around and assembles proteins based on those notes — a process called translation.

RNA regulation

RNA is unstable. As soon as the protein is assembled, the notes are erased, i.e., the RNA molecule falls apart. This instability of RNA is an important feature because as long as the RNA stays in tact, more and more proteins will be assembled (DNA expression). By falling apart relatively quickly, RNA is able to regulate how much protein is translated. If a lot of protein is needed, more RNA molecules will be transcribed from the same section of DNA, leading to the translation of many proteins.

RNA undergoes alternative splicing. Another way RNA regulates the execution of the instructions in the DNA manual, is through a mechanism called alternative splicing. What this means is that a single instruction in DNA can be transcribed into RNA and then, before translation, different sections can be erased, or cut out; the remaining sections then stitch themselves together.

Credit: Agatham

In order to function, our bodies need a lot of different kinds of proteins. If every single protein had its own instruction, we would have far more DNA than the 3 billion nucleotide pairs we already have! There’s a limit to how much material can be contained and maintained. At the same time, if each piece of DNA could only produce a single protein, we wouldn’t have nearly all the proteins we need to carry out essential functions. The fact that the middle man between DNA and proteins, RNA, can be edited, is an ingenious solution.

Types of RNA

Let’s look more closely at two kinds of RNA: mRNA and tRNA.

mRNA is the “notes in pencil” we described above. That’s the RNA that looks almost identical to an original section of DNA, and which after translation, disassembles relatively quickly.

tRNA is a special type of RNA that reads the mRNA and assembles the protein. There are 20 possible amino acids that are used for building proteins. Each of the amino acids is recognized by a unique tRNA molecule. Every group of 3 nucleotides — codons — is recognized by a tRNA, which adds its respective amino acid to the growing chain, until the complete length of the protein has been assembled.


Once the proteins are assembled, they go through some additional modifications, like being folded correctly. Then they are transported to wherever inside or outside of the cell they are meant to carry out the original instruction.

If mistakes are made and the protein doesn’t turn out just right, it is disposed of in cellular garbage cans called proteasomes. Otherwise, it heads off to do its job.

Variability across ethnicities

Interestingly, in some cases, gene expression, or protein levels, differ between ethnicities.

To give you a MyHeritage Ethnicity Estimate, we read your DNA and produce a data file with the information. We don’t read every part of your DNA, which amounts to about 3 billion points. This is an expensive method called whole genome sequencing, currently reserved for specific clinical and research applications. Instead we focus on reading approximately 700,000 locations in your DNA that are known to vary between individuals, called single nucleotide polymorphisms (SNPs, pronounced “snips”). This method is called genotyping and it produces a data file that lists each SNP that we read, its position in your DNA, and the two alleles we found there (i.e. the A, T, G, or C you inherited from each parent). By analyzing your genotypes for certain SNPs, we can estimate what percentage of your DNA is from each ethnicity.

The allele frequency of certain SNPs, e.g., how likely you are to have an A or a T in given positions, is associated with different ethnicities. Some SNPs are associated with how much of a certain gene tends to be expressed. To give just one example, there is a specific protein that is generally found in different amounts in British Caucasian people versus in Jamaican people due to different, ethnicity-associated genotypes.

The Dogma

The process of gene expression — from DNA to RNA to proteins — is called “The Dogma” by scientists. If you’ve been following the DNA Basics blog series so far, you now have an excellent grasp of DNA essentials. We hope you’ll stay with us as we continue to explore interesting DNA concepts in the coming months.

Today in History for 8th February 2018

The Weirdest Winter Olympic Events We No Longer Play

Horse-drawn skiing and ski "ballet" are among the unusual sports from past Olympic games.

February 07 2018


Desperate for Food, Polar Bear Tests Walrus

If unable to find food, one expert says the cub likely died soon after the video was taken.

First Person to Walk Untethered in Space Gives a Final Interview

Astronaut Bruce McCandless offers his thoughts on an iconic photo in his last-ever interview with National Geographic.

What's an 'Earthquake Swarm,' And Is One Hitting Taiwan?

Several people have been killed and dozens remain unaccounted for as a series of quakes rattle the region. But are these earthquakes part of a cycle?

They considered themselves white, but DNA tests told a more complex story

Nicole Persley of Boca Raton, Fla. says a genetic test validated what she had dug up about her family's heritage.

DNA Tests on an Ancient Skeleton Reveal the First Briton Was Black, Not White

"It really shows up that these imaginary racial categories we have... are not applicable to the past at all," said one project worker.

Volcanoes, Then an Asteroid, Wiped Out the Dinosaurs

Several species went extinct before the impact 66 million years ago, adding to evidence that volcanoes were a culprit in the mass die-off.

Here’s what happened when black politicians held power

Study shows how they aided southern blacks during Reconstruction

The unsavory record of the connections between universities and slavery is finally coming to light

From their very beginnings, the American university and American slavery have been intertwined, but only recently are we beginning to understand how deeply.

These Tiny Scales Make Sharks Incredibly Fast. Can They Help Us Build Better Planes?

The scales of shortfin makos, the fastest species of shark, could guide the design of aerial vehicles in the future.

Britain's Dark-Skinned, Blue-Eyed Ancestor Explained

Thanks to technological advances, scientists can see ancient DNA in new detail.

Surprise! Scientists Find That Starfish Eyes Actually See, at Least a Little

After decades of wondering what starfish use their eyes for, it turns out they probably use them to stay close to home, according to a new study.

The Famine Ended 70 Years Ago, but Dutch Genes Still Bear Scars

Babies born during the Dutch Hunger Winter became adults with higher rates of health problems. Now researchers may have found the genetic switches that made it happen.

Inside the London Café Accused of Glorifying ‘Racist’ Winston Churchill

A group of students who invaded the Blighty café in North London, which houses a statue of Winston Churchill, say they were decrying the wartime British prime minister’s racism.

Poland wants to outlaw blaming Poles for Nazi atrocities

But what about the Jedwabne massacre?
Today in History for 7th February 2018
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