90 Fun Facts About RNA

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

Uracil. Thymine is just uracil with a methyl group added; because cytosine can decay into uracil, DNA's repair enzymes treat any uracil they find there as damage and cut it out.

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

A 2' hydroxyl group. That one extra –OH can attack RNA's own backbone, which is why RNA breaks down so much more easily than DNA, the sturdier long-term store.

Which two bases are the purines RNA shares with DNA?

Adenine and guanine. Purines are built on a double ring and pair only with single-ring partners, which keeps every rung of a double helix the same width.

Who discovered nucleic acids in the 1860s and called the material 'nuclein'?

Friedrich Miescher. He found it in pus, washing white blood cells off used bandages that a surgical clinic near his Tübingen laboratory sent over.

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

Ribosomal RNA. It is never translated into protein itself; cells need it in bulk because it is the main building material of ribosomes, which in bacteria hold more RNA than protein.

Which pair, Nobel winners for gene control, coined 'messenger RNA'?

Jacob and Monod. Working at the Pasteur Institute in Paris, they proposed in 1961 that a short-lived RNA copy ferries each gene's instructions out to the ribosomes, where proteins are made.

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

A modified guanine cap. The methylated guanine is joined on backwards, through a rare 5'-to-5' link, and it steadies the message and helps it bind a ribosome.

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

Exonucleases. These enzymes chew an RNA from its ends, and the tail holds them off; oddly, in bacteria a poly(A) tail does the opposite and marks a message for destruction.

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.

Which part of a transfer RNA reads the three-letter words of a messenger RNA?

Anticodon. It is allowed to pair loosely with the third letter of each word, a 'wobble' that lets one transfer RNA read more than one of the 61 coding words.

What does a transfer RNA carry on the CCA tail at its 3' end?

Amino acid. A separate loading enzyme for each of the 20 kinds attaches the right one to the right tRNA, so those enzymes, not the ribosome, are what match each coding word to its meaning.

Unlike DNA with its famous double helix, RNA in cells is usually found in what form?

A single strand. With no partner strand to hold it straight, an RNA can fold back and pair with itself, and those folds give each kind of RNA the shape it needs to work.

Which enzyme copies the DNA of a gene into a strand of RNA?

RNA polymerase. It latches onto a promoter, a short stretch of DNA that marks where a gene begins, parts the two strands and copies one of them until a stop signal knocks it off.

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

George Emil Palade. He described them in 1955 as dense specks studding the cell's inner membranes, then went on to trace the route that newly made proteins take through the cell.

A bacterial ribosome's 50S and 30S subunits join into a 70S whole because Svedberg units measure what?

Sedimentation rate. A Svedberg value records how fast a particle settles in a centrifuge, which depends on its shape as well as its mass, so the two subunits' numbers do not simply add up.

Why are ribosomes classified as ribozymes?

Their catalytic core is RNA. Every bond in a new protein is forged by RNA, while the ribosome's dozens of proteins sit around the surface as scaffolding.

Which protozoan was Thomas Cech studying when he found an RNA that cuts itself?

Tetrahymena. In a test tube with no protein present, a stretch of its RNA cut itself out and rejoined the ends, overturning the rule that every enzyme is a protein.

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

Sidney Altman. He studied RNase P, an enzyme that trims newly made transfer RNAs, and showed that its RNA part can do the cutting on its own, without the protein.

Which self-cutting RNA enzyme, first found in plant pathogens, takes its name from the outline of its folded structure?

Hammerhead. Early diagrams of its three joined helices looked like the head of a hammerhead shark; some plant pathogens use it to cut their freshly copied RNA into single genome lengths.

Which Harvard biologist, a Nobel winner for a way to sequence DNA, coined the term 'RNA world' in 1986?

Walter Gilbert. He only named it: Leslie Orgel and Carl Woese, among others, had argued back in the 1960s that RNA came first, long before any RNA enzyme was found.

Which part of a human cell keeps its own ribosomes and transfer RNAs, a legacy of its bacterial ancestry?

Mitochondria. They descend from bacteria that took up life inside an ancestral cell, and they still carry a tiny genome of 37 genes, most of them recipes for their own RNAs.

Which Nobel-winning tool, borrowed from the immune defences of bacteria, uses a guide RNA to find its target?

CRISPR. Bacteria file away snippets of viruses that once attacked them and copy these into RNA guides, which lead a cutting enzyme to any matching invader; scientists learned to reprogram the guide.

In which part of a human cell is the RNA for new ribosomes produced?

The nucleolus. This dense knot inside the nucleus is a ribosome workshop: it copies the RNA, wraps it in proteins brought in from outside, and sends out the two half-built halves of each ribosome.

Victor Ambros and Gary Ruvkun won the 2024 Nobel Prize for discovering which gene-silencing molecules?

MicroRNAs. The first, found in 1993, was written off as a quirk of one laboratory animal until Ruvkun showed in 2000 that a second is shared across the animal kingdom, humans included.

Fire and Mello's Nobel-winning gene-silencing work used which organism?

Caenorhabditis elegans. Injecting this tiny worm with double-stranded RNA silenced the matching gene where either strand alone did nothing, and the effect spread between cells and even to its offspring.

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

Dicer. True to its name, it dices the long strands into pieces a little over 20 letters long, and each piece then guides a silencing complex to any message that matches it.

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

Petunia. Extra copies of a pigment gene were meant to deepen the colour, but many blooms came out white instead: the added genes had shut down the plant's own along with themselves.

The 2018 drug patisiran was first to exploit which discovery?

RNA interference. Twenty years after the effect was reported in 1998, patisiran used a short double-stranded RNA to silence the faulty gene behind a rare inherited nerve disease.

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

Reverse transcriptase. It runs the cell's usual DNA-to-RNA flow backwards, which is the 'retro' in retrovirus, and blocking it was the basis of AZT, the first approved HIV drug.

Which two scientists independently discovered the enzyme that copies RNA into DNA?

Temin and Baltimore. Temin had proposed years earlier that some RNA viruses write themselves into DNA, against the accepted rule that information flows only the other way; then both men found the enzyme.

HIV belongs to which group of retroviruses?

Lentiviruses. The name is from the Latin 'lentus', slow, for the long delay between infection and illness; unusually, they can infect cells that are not dividing, which has made disarmed versions a favourite vehicle for gene therapy.

A gene from an ancient RNA virus now helps build which human organ?

The placenta. Syncytin, the protein that fuses cells into its outer layer, began as the envelope protein of an ancient retrovirus; such viral remains make up as much as 8% of human DNA.

Which of these diseases is caused by a virus that stores its genes as RNA rather than DNA?

Measles. RNA viruses are sloppy copiers that usually mutate fast, yet measles is the odd one out: it has changed so little that vaccines made from a strain isolated in 1954 still protect.

Blackburn, Greider and Szostak shared the 2009 Nobel Prize for work on which enzyme that rebuilds chromosome ends?

Telomerase. Carol Greider first saw it at work on Christmas Day 1984; the enzyme carries its own scrap of RNA and uses it as the template for rebuilding the tips that wear down as cells divide.

Sharp and Roberts's 1993 Nobel honoured which gene segments, cut from RNA copies?

Introns. Working in 1977 with a virus that causes colds, both men saw that a gene can lie in separate pieces, with the stretches in between snipped out of the RNA and the pieces joined up.

Which cell machine, built from five RNA-protein particles, removes unwanted stretches from RNA messages?

Spliceosome. Its five particles, nicknamed 'snurps', gather on the RNA at each interruption in a gene, snip that stretch out and stitch the two loose ends together.

Which plant pathogens, the smallest known, are nothing but a naked loop of RNA?

Viroids. Only a few hundred letters long and coding for no protein at all, they get a plant's own enzymes to copy them; the first one identified causes a disease of potatoes.

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

Severo Ochoa. His enzyme let researchers build the test RNAs used to work out the genetic code, yet in living cells its real job turned out to be breaking RNA down, not making it.

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

Francis Crick. He later admitted he had not really known what 'dogma' means, and Jacques Monod had to explain it to him: Crick had meant a bold hypothesis, not an article of faith.

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

Modified nucleosides. Lab-made mRNA set off inflammation until they swapped one of its building blocks for a modified version of the kind the body's own RNA carries, which let it slip past the cell's alarms.

Katalin Karikó was born in which country?

Hungary. When her laboratory in Szeged lost its funding in 1985 she left for a research post in Philadelphia, where money for her mRNA work kept running dry for years.

In mRNA vaccines, the RNA is delivered inside what?

Lipid nanoparticles. Bare mRNA is fragile and hard to get into cells, so each strand is wrapped in a tiny bubble of fat that shields it and helps cells take it up.

Which two makers' mRNA COVID-19 vaccines were first authorized in December 2020?

Pfizer–BioNTech and Moderna. Because an mRNA vaccine is built straight from a virus's genetic sequence, both were developed at record speed, and each showed about 95% protection in its trial.

What does the mRNA in a COVID-19 vaccine instruct a person's cells to make?

The spike protein. Cells read the message and display this one harmless piece of the virus's surface, which trains the immune system to recognise the real thing; the mRNA itself is broken down within days.

The RNA Xist shuts down one X chromosome in each cell of a female mammal, producing which cat coat?

Calico. The gene for orange or black fur sits on the X chromosome, so each patch shows which X stayed switched on in that patch of skin; it is why calico cats are almost always female.

The first genome ever sequenced in full, in 1976, belonged to which RNA virus of bacteria?

Bacteriophage MS2. Walter Fiers's laboratory in Ghent read its coat-protein gene in 1972, the first gene ever sequenced, then spent four more years finishing the rest of the small RNA genome.

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

Transcription. He first came to Stockholm aged twelve to watch his father Arthur collect a Nobel Prize; 47 years later his own crystal pictures caught the gene-copying machinery in full action.

AUG, the usual 'start' signal on a messenger RNA, also spells out which amino acid?

Methionine. Because the start signal doubles as its code word, nearly every protein is born with a methionine at the front, though cells often trim it off afterwards.

Robert Holley won a 1968 Nobel Prize for the first full sequence of a nucleic acid, a transfer RNA from which organism?

Yeast. Holley's Cornell team spent years just purifying this one small RNA from it; the result, published in 1965, was the first complete sequence of any nucleic acid, DNA included.

Where is a eukaryotic messenger RNA translated into protein?

In the cytoplasm. A finished message has to be shipped out to the ribosomes there; bacteria skip that step, so their ribosomes start reading a message while it is still being copied.

In a human cell, where is a gene transcribed into messenger RNA before the message is shipped out?

In the nucleus, a surrounding membrane keeps transcription apart from translation, so the RNA copy can be finished and checked before any ribosome reads it.

With four RNA bases read three at a time, how many different codons does the genetic code contain?

64 comes from four times four times four; a two-letter code would give only 16 words, too few to name every amino acid a cell uses.

Alpha-amanitin, a toxin that halts messenger RNA production, is the chief poison of which mushroom?

Death cap is behind most fatal mushroom poisonings, and cooking is no defence: its toxins survive both heat and freezing.

Which antibiotic, the first cure for tuberculosis, makes bacterial ribosomes misread their messages?

Streptomycin was isolated in 1943 by PhD student Albert Schatz, who sued for a share of the credit, yet the 1952 Nobel Prize went only to his lab chief, Selman Waksman.

Which type of mutation, caused by adding or deleting one DNA base, garbles every codon downstream?

Frameshift errors do so much damage because codons are read in threes with no spacing, so one slipped letter regroups every later triplet; the earlier it strikes, the more of the protein is altered.

In which organisms can ribosomes start translating a messenger RNA that is only half transcribed?

Prokaryotes translate messages while they are being made, and bacteria lean on that coupling to finish copying their genes and to control how long each message lasts.

The operon model of gene switching was worked out in E. coli genes for digesting which sugar?

Lactose was the cue in the first operon ever described: with none around, a repressor protein blocks the genes, so E. coli wastes nothing on enzymes it cannot use.

Which amino acid, blamed for sleepiness after a turkey dinner, is spelled by just one codon?

Tryptophan is spelled only by UGG, and the turkey story is a myth: the bird holds no more of it than other poultry.

Which stretch of DNA beside a gene, often holding a TATA box, marks where transcription starts?

Promoter regions sit beside the gene they control, and in bacteria they carry two short landmarks about 10 and 35 bases ahead of the starting point.

A ribosome's three slots for transfer RNA are labelled A, P and E; what does the E stand for?

Exit is the last stop for a spent transfer RNA: once its cargo has joined the growing chain, the emptied carrier shuffles along and drops off the ribosome.

Stop codons UAG and UAA were nicknamed amber and ochre; which gemstone name was given to UGA?

Opal kept a running joke going: 'amber' honoured a Caltech student called Bernstein, whose surname is German for amber, and the later stop signals were named to match.

Which DNA elements can act on a gene from thousands of bases away by looping over to its start?

Enhancers can sit as much as a million base pairs from the gene they control, upstream or downstream, and the DNA in between simply loops out of the way.

In E. coli, which detachable protein guides the RNA-making enzyme to the start of a gene?

Sigma factor comes in several versions, and a bacterium swaps them to switch on whole sets of genes at once, such as the heat-shock version that helps it survive high temperatures.

Which American, working with Heinrich Matthaei, cracked the first codon using an RNA made only of U?

Marshall Nirenberg's all-U message yielded a chain of just one amino acid, phenylalanine, in a test tube run at 3 am in May 1961, proving that UUU was its code word.

Which term describes the genetic code's habit of spelling one amino acid with several codons?

Degenerate here means redundant, not broken: because spare codons spell the same amino acid, many one-letter DNA mutations leave the finished protein unchanged.

Which hypothesis explains how one transfer RNA can read several codons that differ at the third base?

Wobble, named for the slight play at that third position, is why most organisms manage with fewer than 45 kinds of transfer RNA instead of one for every codon.

Which tuberculosis drug, known for turning tears orange, works by blocking bacterial transcription?

Rifampicin physically blocks the bacterial enzyme as it tries to lengthen a new RNA, and resistance arises so quickly that it is almost always paired with other antibiotics.

Which name is given to the DNA strand that is not transcribed but matches the messenger RNA?

Coding, or 'sense', is the label for the strand the enzyme leaves alone: it reads the partner strand instead, so the new RNA comes out as a copy of this one.

In bacteria, which folded shape in a new RNA, followed by a run of Us, makes transcription stop?

A hairpin rich in G–C pairs snaps shut in the fresh transcript, and the strain breaks the weak U–A pairs behind it, freeing the RNA from the DNA.

Which Big Bang physicist founded the RNA Tie Club to work out how genes spell proteins?

George Gamow sent each member a woollen tie embroidered with an RNA spiral and promised a gold tiepin bearing the abbreviation of one amino acid.

Every protein in the human body is strung together from how many standard amino acids?

20 is the standard set, though two rarer extras, selenocysteine and pyrrolysine, are slipped in by special machinery in some organisms.

Which bond, formed with the loss of a water molecule, links each amino acid to the next?

Peptide links behave partly like double bonds, so each one lies flat and cannot twist, which limits the shapes a protein chain can take.

Which muscle protein, one chain of about 34,000 amino acids, acts as a molecular spring?

Titin takes its name from the Titans of Greek myth, and its full chemical name, at 189,819 letters, is sometimes called the longest word in English.

Which helper proteins, many classed as heat shock proteins, stop new chains from clumping together?

Chaperones mostly carry no folding instructions of their own: they simply hold on to half-folded chains until the rest of the protein has been made.

Which DeepMind system, honoured by a 2024 Nobel Prize, predicts a protein's shape from its sequence?

AlphaFold had by 2022 supplied predicted shapes for around 200 million proteins, nearly every one known, where sixty years of lab work had solved only about 170,000.

Which cattle illness of 1990s Britain is caused not by a germ but by a misfolded protein, a prion?

Mad cow disease, or BSE, spread through feed made from the remains of infected animals, and British vets diagnosed more than 180,000 cattle before it faded.

Which coiled protein shape did Linus Pauling fold from a strip of paper while in bed with a cold?

Alpha helix turned out to be the commonest fold in proteins, a coil pinned in shape by hydrogen bonds between one turn and the next.

Ribosomes that make proteins for export sit studded across the surface of which membrane system?

Endoplasmic reticulum dotted with ribosomes is called 'rough' for its grainy look, while the bare 'smooth' kind makes fats and steroid hormones instead.

Which organelle, a stack of flattened sacs, packages newly made proteins into vesicles for delivery?

Golgi apparatus stacks are named after Camillo Golgi, the Italian who spotted them in 1898, and a typical mammal cell holds 40 to 100 of them.

Which hormone is first built as one long chain, then cut so that its middle section falls away?

Insulin starts life as proinsulin, a chain of 86 amino acids whose connecting stretch holds the two ends in place while sulfur bridges form between them.

A hair perm breaks and re-forms the sulfur bridges between units of which amino acid in keratin?

Cysteine makes up roughly 14% of human hair, and the same sulfur cross-links make nails, hooves and claws even harder.

What name is given to a string of ribosomes all reading one messenger RNA, like beads on a thread?

Polysome clusters explain how a cell gets by with so little messenger RNA: several ribosomes work along the same message at once. They were first dubbed 'ergosomes' in 1963.

Which enzymes load every transfer RNA with its correct cargo before it reaches the ribosome?

Aminoacyl-tRNA synthetases are where the genetic code is really enforced, and some proofread their own work, undoing a wrong match before it can reach the ribosome.

Which energy molecule, a cousin of ATP, do a ribosome's helper proteins burn during translation?

GTP is split each time the ribosome shifts one codon along its message, part of a hefty energy bill for every protein a cell builds.

Which proteins, rather than any transfer RNA, recognise a stop codon and end translation?

Release factors were assumed to be a special transfer RNA until Mario Capecchi showed in 1967 that the stop signal is read by a protein instead.

Proteins are built in one direction only; which end of the chain leaves the ribosome first?

N-terminus first is why the address tags that steer a protein to its destination usually sit at that end, ready to be read while the rest is being made.

Which Israeli crystallographer shared a 2009 Nobel Prize for mapping the ribosome atom by atom?

Ada Yonath chased the ribosome's structure for over twenty years in the face of widespread scepticism, and became the first woman in 45 years to win the chemistry prize.

Which vaccine-preventable infection's toxin kills cells by jamming the ribosome's elongation factor?

Diphtheria toxin welds a chemical tag onto elongation factor 2, so the stricken cell can no longer extend any protein chain and dies.

Which chemist shared a 1972 Nobel Prize for showing that an unfolded enzyme can refold unaided?

Christian Anfinsen unravelled the enzyme ribonuclease with chemicals and watched it regain its activity, a sign that the folding recipe is written into the chain itself.

Which biologist won a 1999 Nobel Prize for showing that proteins carry built-in address tags?

Günter Blobel gave all of his prize money to the rebuilding of Dresden, including its Frauenkirche, a city he had first seen as a child refugee fleeing Silesia in 1945.