50 Fun Facts About RNA

Which base does RNA use in place of DNA's thymine?

Thymine is just uracil with a methyl group added, which makes DNA more stable and easier to proofread.

Which feature of the ribose sugar chemically distinguishes RNA from DNA?

That extra –OH makes RNA more reactive and pushes its helices into the A-form rather than DNA's B-form.

Which two RNA bases are purines?

Purines have a double ring; the single-ring pyrimidines in RNA are cytosine and uracil.

Who discovered nucleic acids in 1868 and called the material 'nuclein'?

He isolated it from pus-soaked bandages collected from a surgical clinic in Tübingen.

Which type of RNA makes up about 80% of the RNA in most cells?

It is never translated into protein itself, yet it forms the catalytic core of every ribosome.

Who coined the term 'messenger RNA'?

Brenner and Crick conceived the idea in April 1960 while Jacob described the PaJaMo experiment to them.

What is added to the 5' end of a eukaryotic messenger RNA soon after it starts being made?

The 7-methylguanosine cap protects the message and helps ribosomes find its start.

What does the poly(A) tail on a messenger RNA chiefly protect it from?

Oddly, in bacteria a poly(A) tail does the opposite and speeds degradation.

The secondary structure of transfer RNA is usually drawn in what shape?

In three dimensions the cloverleaf folds into an L shape that slots into the ribosome's A and P sites.

What three-nucleotide sequence on a transfer RNA pairs with a codon?

Some anticodons pair with more than one codon thanks to 'wobble' at the third position.

Which three-letter tail at the 3' end of a transfer RNA carries the amino acid?

Cytosine-cytosine-adenine is the universal attachment point; in many organisms it is added after transcription.

Transfer RNA was formerly known by what name?

Crick had predicted an 'adaptor' molecule, and the small soluble RNA in the cytoplasm turned out to be it.

Who discovered transfer RNA in 1958?

Robert Holley then worked out the full sequence of yeast alanine tRNA in 1965 and won a Nobel for it.

Who first observed ribosomes in the mid-1950s with an electron microscope?

He shared the 1974 Nobel Prize with Claude and de Duve for mapping the cell's internal structure.

A bacterial 70S ribosome is made of which two subunits?

Svedberg units measure sedimentation rate, not size, which is why 50 plus 30 equals 70.

Why are ribosomes classified as ribozymes?

The peptidyl transferase reaction that links amino acids is performed by the RNA, not the proteins.

Which protozoan was Thomas Cech studying when he found self-splicing RNA?

The intron in a ribosomal RNA gene cut itself out with no protein involved at all.

Who shared the 1989 Nobel Prize in Chemistry with Cech for discovering catalytic RNA?

Altman found the catalytic RNA inside RNase P, the complex that matures pre-tRNAs.

Which of these is a named ribozyme?

Others include the hairpin ribozyme, the VS ribozyme and the leadzyme.

Who coined the term 'RNA world' in 1986?

Alexander Rich had floated the concept back in 1962, and Woese's 1967 book The Genetic Code discussed it too.

In the RNA world hypothesis, RNA filled which two roles now split between DNA and proteins?

The ribosome, an RNA enzyme at the heart of every cell, is seen as a surviving relic of that era.

The first microRNA, lin-4, was discovered in which organism?

It controls developmental timing in C. elegans and was assumed for years to be a worm oddity.

Roughly how long is a mature microRNA?

Dicer trims the hairpin precursor down to a short duplex that then guides gene silencing.

Victor Ambros and Gary Ruvkun won the Nobel Prize for microRNA in which year?

It came more than 30 years after their back-to-back lin-4 papers in 1993.

Fire and Mello's Nobel-winning RNA interference work used which organism?

Their 1998 paper showed double-stranded RNA, not single-stranded, was the trigger for silencing.

Which enzyme chops long double-stranded RNA into short siRNAs?

The fragments are 21 to 23 nucleotides long and load into the RISC complex to find their targets.

Early RNA-silencing clues came from trying to deepen the colour of which flower?

Adding extra pigment genes produced white patches instead — the genes were switching each other off.

What was the first siRNA-based medicine, approved in 2018?

Alnylam's drug, sold as Onpattro, was also the FDA's first approval of lipid nanoparticles as a delivery system.

Which enzyme lets a retrovirus copy its RNA genome into DNA?

The 'retro' in retrovirus refers to this backward flow of information, the reverse of the usual pattern.

Which two scientists independently discovered the RNA-to-DNA copying enzyme in 1970?

They shared the 1975 Nobel Prize with Renato Dulbecco; the discovery overturned a simple reading of the central dogma.

Which class of retrovirus includes HIV-1 and HIV-2?

The name means 'slow viruses', for the long delay between infection and disease.

Endogenous retroviruses make up roughly what share of the human genome?

They are fossils of ancient infections that got into the germ line and have been inherited ever since.

Which enzyme extends chromosome ends using its own built-in RNA template?

It is technically a reverse transcriptase, and its RNA component was first found in Tetrahymena in 1984.

Szostak, Greider and Blackburn won the 2009 Nobel Prize for discovering what?

Greider found the enzyme on Christmas Day 1984 as Blackburn's graduate student.

Introns and RNA splicing were discovered in which year?

Philip Sharp and Richard Roberts found the 'split genes' in adenovirus and shared the 1993 Nobel Prize.

The spliceosome is built from how many small nuclear ribonucleoproteins?

U1, U2, U4, U5 and U6 assemble on each intron, making splicing one of the most complex steps in gene expression.

Most introns begin and end with which two-letter sequences?

The GU-AG rule marks the 5' and 3' splice sites; introns that break it are handled by a minor spliceosome.

Who won the 1959 Nobel Prize for an enzyme that could make RNA in the lab?

The enzyme, polynucleotide phosphorylase, was later shown to break RNA down rather than build it.

Who first stated the 'central dogma' of molecular biology in 1957?

He published it in 1958; the core idea is that information cannot flow from protein back into nucleic acid.

Karikó and Weissman won the 2023 Nobel Prize for work on what?

Swapping uridine for modified versions stopped the immune system from destroying synthetic mRNA on sight.

Katalin Karikó was born in which country?

The University of Pennsylvania demoted her in 1995 after repeated grant rejections; she later became a BioNTech senior vice president.

In mRNA vaccines, the RNA is delivered inside what?

The fatty shells protect the fragile strands and help cells absorb them.

In which month did the Pfizer–BioNTech and Moderna mRNA vaccines receive authorization?

SARS-CoV-2 had been sequenced only at the start of that year; Pfizer's shot needed ultracold storage, Moderna's did not.

Which modified base replaces uridine in many mRNA vaccines to reduce toxicity?

It makes the synthetic message look less foreign and translate more efficiently.

The long non-coding RNA Xist drives which process?

It coats one X chromosome in female mammals and silences it into a Barr body.

The first complete genome sequence of an RNA virus, in 1976, was of what?

Walter Fiers's team in Belgium read all 3,569 nucleotides by hand — a year before Sanger sequenced a DNA genome.

Roger Kornberg's 2006 Nobel Prize recognized images of which process?

His father Arthur had shared the 1959 prize with Ochoa, making them a rare parent-child Nobel pair.

Which sequence is the most common start codon on a messenger RNA?

It codes for methionine, so nearly every newly made protein begins with that amino acid.

Robert Holley's 1968 Nobel Prize came for sequencing 77 nucleotides of what?

It took him seven years and about a ton of yeast to purify enough alanine tRNA to read.

Where is a eukaryotic messenger RNA translated into protein?

Bacteria lack the compartments, so their ribosomes can start translating a message while it is still being transcribed.