98 Fun Facts About Genetics

Which shape did James Watson and Francis Crick propose for the structure of DNA in 1953?

Double helix: months earlier Linus Pauling had proposed a triple helix for DNA, a model he soon saw was built inside out with the wrong number of strands.

Gregor Mendel belonged to which religious order?

Augustinians: Mendel joined their St Thomas's Abbey in Brno, and once he became abbot in 1868 his administrative duties largely ended his experiments.

Roughly how many plants did Mendel cultivate and test between 1856 and 1863?

28,000: most were garden peas, and when Mendel later tried hawkweed his results would not repeat, because hawkweed's seeds grow into clones of the mother plant.

Which naturalist died in 1882 without ever reading Gregor Mendel's work on pea hybrids?

Charles Darwin was unaware of Mendel's paper and tried instead to explain heredity with his own theory, pangenesis, which never worked out.

Who coined the word 'genetics' for the study of heredity?

William Bateson championed Mendel's rediscovered laws so fiercely against rivals such as W. F. R. Weldon that he was nicknamed 'Mendel's bulldog'.

Who introduced the word 'gene' for a unit of heredity?

Wilhelm Johannsen found that sowing only the biggest beans from a pure line didn't breed bigger beans, which led him to split genotype from phenotype.

What idealized phenotype ratio did Mendel find in monohybrid crosses?

3:1: R. A. Fisher later showed that many genes, each inherited in such ratios, add up to the smooth bell-curve variation seen in many traits.

Which principle explains why round green peas appeared in the second generation after Mendel crossed round yellow with wrinkled green?

Law of independent assortment has a physical cause: chromosome pairs line up at random as sex cells form, so genes on different chromosomes are shuffled separately.

The Punnett square is named after a geneticist from which country?

Britain: Cambridge geneticist Reginald Punnett took a population puzzle to his cricket partner G. H. Hardy, whose answer became the Hardy–Weinberg principle.

Which base pairs with adenine in DNA?

Thymine: Erwin Chargaff found DNA holds about as much adenine as thymine, a clue Watson and Crick explained by pairing the two bases.

Which inheritance pattern explains the AB blood type?

Codominance puts both A and B markers on red blood cells, so AB plasma carries neither anti-A nor anti-B antibodies and can be given to patients of any blood group.

What term describes one gene masking the effect of another?

Epistasis is why a yellow Labrador can carry the gene for a black coat: two copies of a recessive e allele keep black pigment out of its fur.

Who showed that genes sit on chromosomes after spotting a white-eyed mutant male in 1910?

Thomas Hunt Morgan had been skeptical of Mendel's laws, until the white-eyed trait proved to be sex-linked, tying a gene to a sex chromosome.

Genes lying close together on a chromosome are rarely separated by which event during meiosis?

Crossing over separates distant genes more often than close ones, and undergraduate Alfred Sturtevant used those rates to draw the first genetic map.

Which insect is the model organism known by the name Drosophila melanogaster?

The fruit fly breeds a new generation in about ten days, so geneticists can follow a trait through several generations within weeks.

The word 'chromosome', coined in 1888, literally means what?

Coloured body: the structures were named for how strongly they take up the dyes used to stain cells.

How many chromosomes does a typical human cell contain?

46: egg and sperm cells each carry a single set of 23, so fertilization restores the full set in every new human.

What is the name for an image of a cell's chromosomes arranged in pairs by size?

Karyotype: ones made with better techniques by Joe Hin Tjio and Albert Levan in the mid-1950s overturned a human chromosome count repeated for some 30 years.

Duplicated copies of a chromosome joined at the centromere are called what?

Sister chromatids are pulled to opposite ends of a dividing cell, so each daughter cell receives an identical copy of every chromosome.

Which bacteriologist studying pneumonia discovered bacterial 'transformation' in 1928?

Frederick Griffith saw harmless pneumococci turn deadly when mixed with heat-killed virulent ones, and in 1944 Oswald Avery's team showed the transforming agent was DNA.

Which PhD student worked with Rosalind Franklin on the famous X-ray image 'Photo 51'?

Raymond Gosling had started out under Maurice Wilkins, who later showed the image to James Watson.

Why could Rosalind Franklin not share the 1962 Nobel Prize for the structure of DNA?

She had died four years earlier, and Nobel rules then barred awards to anyone not nominated while alive, so Watson, Crick and Wilkins shared it.

Which molecule carries a gene's instructions from the nucleus to the ribosomes?

Messenger RNA is what the Pfizer–BioNTech and Moderna COVID-19 vaccines delivered, so cells briefly made the virus's surface protein and built immunity to it.

Which codon is the most common start signal, read as methionine?

AUG is where ribosomes begin translating, so nearly every newly made protein starts with methionine, or formylmethionine in bacteria and mitochondria.

Which inherited disorder did Queen Victoria pass into royal families across Europe?

Haemophilia afflicted Russia's heir Alexei, and the imperial family came to rely on the mystic Rasputin, who seemed able to ease his bleeding.

Which enzyme, from a hot-spring bacterium, made PCR practical?

Taq polymerase comes from a bacterium first found in a Yellowstone hot spring, so it survives the high heat that separates DNA strands in each PCR cycle.

Who invented PCR in 1983?

Kary Mullis said the idea came to him on a Friday-night drive from Berkeley to his cabin in Mendocino, and it won him a share of the 1993 Nobel Prize in Chemistry.

Who developed chain-termination DNA sequencing in 1977?

Frederick Sanger won his second Nobel Prize in Chemistry for it, yet he declined a knighthood because he did not want to be addressed as 'Sir'.

Which geneticist succeeded James Watson in 1993 as head of the Human Genome Project?

Francis Collins led it under the Bermuda Principles, which had labs post new human DNA sequence publicly, preferably within 24 hours.

Which company launched a rival private human genome effort in 1998?

Celera Genomics vowed to finish years sooner, so the public Human Genome Project moved its own completion date forward to 2003.

Which two leaders jointly announced the rough draft of the human genome in June 2000?

Clinton and Blair announced that the public project and its private rival had both finished drafts, after the two sides agreed to a truce.

About how many protein-coding genes does the human genome contain?

About 20,000: alternative splicing joins a gene's exons in different combinations, so humans make many more distinct proteins than they have genes.

Why do chimpanzees have one more pair of chromosomes than humans do?

Two chromosomes fused in our ancestors, and human chromosome 2 still carries a leftover second centromere from the join.

Which consortium published the first truly complete human sequence in 2022?

Telomere-to-Telomere filled the gaps the Human Genome Project left, mostly repetitive DNA near chromosome centres and ends that short DNA reads couldn't place.

Which serial killer was caught in 2018 after investigators traced crime-scene DNA through relatives on a genealogy website?

The Golden State Killer turned out to be former police officer Joseph DeAngelo, found by building a family tree from distant cousins on the site GEDmatch.

A mutation caused by inserting or deleting bases not divisible by three is called what?

Frameshift mutations change how every later codon is read, often creating an early stop signal that leaves the protein abnormally short.

Which astronaut's year in space was compared with the genes of his identical twin on Earth?

Scott Kelly spent 340 days in space while his twin Mark stayed on Earth as the control, and some genes whose activity changed in space had still not returned to normal six months after landing.

Barbara McClintock won the 1983 Nobel Prize for discovering what in maize?

Genetic transposition: McClintock saw genes jump around maize chromosomes and change kernel colours, and her Nobel came more than 30 years after the discovery.

Dolly the sheep was cloned from a cell taken from which organ?

Mammary gland: that is why the Roslin team named her after singer Dolly Parton, since Ian Wilmut said they couldn't think of a more impressive pair of glands.

Emmanuelle Charpentier and Jennifer Doudna's Nobel-winning CRISPR gene-editing tool is nicknamed what?

Genetic scissors: the tool was borrowed from an ancient bacterial immune system that disarms invading viruses by cutting up their DNA.

The widely used Cas9 enzyme comes from which bacterium?

Streptococcus pyogenes, the germ behind strep throat, is where Emmanuelle Charpentier found tracrRNA, a key piece of the CRISPR system.

Casgevy, the first approved CRISPR medicine, treats sickle-cell disease and which other condition?

Beta thalassemia: Casgevy edits a patient's own bone marrow stem cells so the body can make working haemoglobin, and regulators first licensed it in November 2023.

Down syndrome is caused by an extra copy of which chromosome?

21: most cases begin with an error as an egg or, less often, a sperm cell forms, so the child inherits an extra copy of chromosome 21 in every cell.

Which American folk singer died of Huntington's disease in 1967?

Woody Guthrie's former wife Marjorie founded a group in 1967 that grew into the Huntington's Disease Society of America.

Cystic fibrosis follows which inheritance pattern?

Autosomal recessive: carriers with one faulty copy are usually healthy, but two carrier parents have a one-in-four chance with each pregnancy of a child with the disease.

Which sex-determination system do most birds use?

ZW: in birds the female carries the two different sex chromosomes, so the egg, not the sperm, decides whether a chick is male or female.

In humans, which gene on the Y chromosome triggers male development?

Even an XXY individual develops as male because of it; the platypus manages without SRY entirely.

In alligators and some turtles, what determines the sex of the offspring?

Incubation temperature: in sea turtles warmer nests hatch more females, so global warming has already tipped some populations heavily toward females.

Which feature, shaped partly by contact with the womb, differs even between identical twins with matching DNA?

Fingerprints differ even in identical twins, because each fetus touches different parts of the womb as the ridges form. The patterns come out similar but never the same.

Carrying one copy of the sickle-cell gene gives a person some protection against which mosquito-borne disease?

Malaria kills fewer of the people who carry a single sickle-cell gene, which is why the gene is commonest where the parasite is. Inheriting two copies brings sickle-cell disease instead.

Which video-game character lends a name to a gene that organises the limbs and nervous system of embryos?

Sonic the Hedgehog gave the sonic hedgehog gene its name, while its sister genes, desert hedgehog and Indian hedgehog, were named after real species. The gene helps lay out limbs and digits.

Which cats are almost always female, because the gene for orange fur sits on the X chromosome?

Calico cats need two X chromosomes to show orange and black patches together, one colour from each. The rare males owe their coats to unusual conditions such as an extra X.

Which English king, dug up beneath a Leicester car park in 2012, was identified by DNA from living relatives?

Richard III was confirmed when DNA from the bones matched two descendants of his sister Anne of York, 17 and 19 generations on. The grave had been lost for more than 400 years.

A variant near the smell-receptor gene OR6A2 is linked to which herb tasting like soap to some people?

Coriander (cilantro) owes its soapy note to aldehydes in the leaves, substances that can also turn up in soap and in stinkbug secretions. In a survey of young adults in Canada, dislike ran from 3% to 21% by ancestry.

The vast majority of bananas traded between countries are genetically identical clones of which variety?

Cavendish bananas cannot reproduce sexually, so every plant is a clone and the crop has very little genetic diversity. That leaves all of them open to the same fungal diseases.

Generations of marriage between close relatives left which European royal dynasty with a famously jutting jaw?

The Habsburgs intermarried so often that the protruding lower jaw can be traced through the family portraits. Charles II of Spain is said to have had the most pronounced case on record.

A 2003 study proposed that about 16 million men carry a Y chromosome inherited from which conqueror?

Genghis Khan was the study's suggested source for a lineage found in about 8% of men from northeast China to Uzbekistan. Later ancient-DNA work has cast doubt on the link.

The Fugate family of Kentucky became famous for a rare inherited condition that turned the skin which colour?

Blue skin appeared in four of the children of Martin Fugate and Elizabeth Smith, who both carried the same rare gene. A doctor later eased the colour with a dye, methylene blue.

Which ABO blood type shows up only when a child inherits the same masked gene version from both parents?

Type O needs two matching copies because the A and B versions each override it. That is how a couple with type A and type B blood can still have a type O child.

Which cell structures hold a small genome of DNA that is inherited almost entirely from the mother?

Mitochondria come only from the egg, because those carried by the sperm are usually destroyed after fertilisation. Their DNA lets researchers trace a maternal line far back in time.

Which inherited condition affects up to 1 in 12 men, because the genes involved lie on the X chromosome?

Colour blindness in its commonest form comes from light-sensor genes on the X chromosome, and a man has no second X to cover a faulty copy. A woman needs the variant on both of hers.

Mutations that spread among cattle-herding peoples let many adults keep digesting which sugar?

Lactose is broken down by an enzyme that most mammals all but stop making after weaning. Up to 96% of north-west Europeans keep making it for life, against 17% of Greeks.

Variants of the MC1R gene on chromosome 16 are responsible for which natural hair colour?

Red hair is most common in people who inherit an MC1R variant from both parents, and the same variants make skin hard to tan. Two brown-haired parents who each carry one copy can have a red-haired child.

A single DNA letter in the ABCC11 gene decides whether a person has the wet or the dry type of what?

Earwax comes out sticky and brown or dry and flaky depending on one change in ABCC11, which also affects underarm odour. The dry type is most concentrated in East Asia.

Which wild cat is so genetically uniform that skin grafts between unrelated animals heal without rejection?

Cheetah genes vary so little that the animals accept each other's skin as if it were their own. The sameness is thought to date from two ancient crashes in their numbers.

Ernest Hemingway's beloved cats gave a nickname to felines born with which dominantly inherited trait?

Extra toes pass down so reliably that a kitten needs only one polydactyl parent to inherit them. After his death in 1961 his Key West house became a museum and a home for his cats' descendants.

Mules are usually sterile because horses and donkeys, the two parent species, differ in what?

Chromosome number is the snag: a horse has 64 and a donkey 62, so a mule gets an odd 63 that cannot split evenly into eggs or sperm. A few female mules have still given birth.

Albinism, which leaves rabbits and mice with white fur and pink eyes, is a lack of which pigment?

Melanin is the only pigment most mammals have, so one broken gene for making it can leave an animal white from nose to tail. The eyes look pink because blood vessels show through an iris with no colour of its own.

Which hormone became, in 1982, the first medicine made by bacteria carrying a human gene?

Insulin made by E. coli carrying human DNA went on sale in 1982 as Humulin. Before that it came from the pancreases of pigs and cows, and eight ounces could take two tons of pig parts.

Flavr Savr, the first genetically engineered food licensed for people to eat, was a variety of which crop?

Tomato shelf life was the target: Flavr Savr was engineered to stay firm for longer after ripening. It went on sale in 1994 and production had stopped by 1997.

The 'immortal' HeLa cells grown in laboratories worldwide since 1951 were taken from which woman?

Henrietta Lacks was 31 when the cells were taken from her cervical tumour without her knowledge. For years the line was wrongly credited to a 'Helen Lane' or 'Helen Larson'.

Angelina Jolie's 2013 article about her preventive double mastectomy drew wide attention to which gene?

BRCA1 was the gene Jolie carried in a faulty form, giving her an estimated 87% risk of breast cancer. Her announcement set off widespread discussion of genetic testing.

Modern Europeans and East Asians carry roughly 2% of DNA from which extinct human relatives?

Neanderthals interbred with modern humans, and about 20% of their genome survives today, scattered in small pieces through living people. Most of what remains does not code for anything.

Genetic tests on royal mummies suggested the parents of which Egyptian pharaoh were brother and sister?

Tutankhamun's parents appear to have been full siblings, both children of Amenhotep III and Queen Tiye. Some Egyptologists read the same results as three generations of cousin marriage.

DNA from which British royal helped confirm the remains of Russia's murdered Romanov family in 1993?

Prince Philip was related to the Romanovs through all four of his grandparents, and his DNA matched the bones more than seventy years after the family was killed.

Up to 8% of the human genome is leftover DNA from ancient infections by what?

Viruses that slipped their genes into our ancestors' egg-making and sperm-making cells left tens of thousands of pieces behind. Each has been inherited ever since like any other stretch of DNA.

Which French naturalist argued that traits gained in life, like a giraffe's stretched neck, pass to offspring?

Lamarck imagined giraffes lengthening their necks by reaching for high leaves, then having young with slightly longer necks. His name stuck to the idea, which fell from favour once Mendel's genetics took hold.

Which type of cell division gives two genetically identical daughter cells, letting the body grow and heal?

Mitosis keeps the chromosome count the same in every new cell, so the parent cell first has to make a copy of each chromosome. The copies are then shared out equally.

What name is given to the alternative versions of one gene, such as those giving purple or white pea flowers?

Alleles are variants of the same stretch of DNA, and the word is short for 'allelomorph', meaning 'other form'. A person inherits one from each parent for most genes.

A pea plant carrying one tall and one short version of the height gene is described by which term?

Heterozygous organisms carry two different versions of a gene. A plant like this one grows tall, yet it can still hand the short version on to its offspring.

Sperm and egg cells hold a single set of chromosomes instead of the usual two, a state described by which term?

Haploid cells hold exactly half the usual chromosome count, one from each pair. When sperm and egg fuse, the new cell is back to a full double set, half from each parent.

What is the name for the one-celled first stage of a new organism, formed when a sperm fertilises an egg?

Zygote is the term, taken from the Greek for 'joined' or 'yoked'. The one cell holds a complete set of instructions and divides again and again to build the whole body.

Each three-letter 'word' of the genetic code tells a cell to add one of which building blocks?

Amino acids come in just 20 standard kinds, while four bases read three at a time give 64 possible words. That is why most of them are spelled by more than one word.

Stretched out end to end, the DNA packed into a single human cell would measure about how long?

About 2 metres of DNA, 1.8 by one estimate, fits inside each cell. Wound around protein spools, it packs into a nucleus only thousandths of a millimetre across.

Which Australian mammal has ten sex chromosomes, where nearly all other mammals make do with two?

Platypus males carry five X and five Y chromosomes, a discovery made in 2004 at the Australian National University. Females have five pairs of X chromosomes instead.

Which members of a honeybee colony hatch from unfertilised eggs and so have a mother but no father?

Drones grow from eggs the queen leaves unfertilised, so each one carries only her genes. A drone has no stinger, and its only role is to mate with a new queen.

A Soviet experiment begun in the 1950s bred which wild animal purely for tameness, with dog-like results?

Silver fox cubs were picked each generation only for showing the least fear of people. Their descendants still grew more dog-like in looks, with mottled or spotted coats.

Which seedless fruit grows on sterile triploid plants, raised by crossing two-set and four-set parents?

Watermelon without seeds was first developed by Japanese scientists in 1939. By 2014 the seedless kind made up nearly 85% of the watermelons sold in the United States.

Gregor Mendel twice failed the exam to qualify for which profession, in 1850 and again in 1856?

Teacher certification escaped Mendel both times, yet he taught physics at a Brno school for 14 years as a substitute. His pea experiments began in the year of the second failure.

Hershey and Chase confirmed in 1952 that DNA carries heredity, using phages and which kitchen appliance?

A blender shook the empty phage coats off infected bacteria, showing that the DNA had gone inside while the protein stayed outside. The work is still nicknamed the Blender experiment.

Friedrich Miescher first isolated DNA in 1869 from white blood cells washed off what at a nearby hospital?

Used bandages were his source because the pus on them was full of white blood cells, from whose nuclei he drew a substance he named nuclein. The hard part was washing the cells off unharmed.

Francis Crick interrupted lunch at which Cambridge pub in 1953 to announce 'the secret of life'?

The Eagle marks the moment with a plaque by its entrance. Its ceiling still carries the names and squadron numbers that Allied airmen burned into it during the Second World War.

Which quantum physicist's 1944 book on the physics of living cells inspired both James Watson and Francis Crick?

Erwin Schrödinger based the book on public lectures he gave in Dublin in 1943, picturing genetic information stored in an 'aperiodic solid'. Crick wrote to him in 1953 about its influence.

Which King's College London biophysicist shared the 1962 Nobel Prize with James Watson and Francis Crick?

Maurice Wilkins was born in New Zealand and worked on isotope separation for the Manhattan Project during the war. He then turned to X-ray studies of DNA in London.

Which Soviet agronomist, backed by Stalin, led a campaign that all but destroyed genetics research in the USSR?

Trofim Lysenko branded modern genetics a 'bourgeois pseudoscience', and more than three thousand biologists were dismissed or imprisoned. His former mentor Nikolai Vavilov died in prison.

Which Victorian polymath coined the word 'eugenics' in 1883 and pioneered the comparison of twins?

Francis Galton also popularised the phrase 'nature versus nurture'. His 1875 paper, The History of Twins, was built on answers to questionnaires he had sent out.

Which geneticist stumbled on DNA profiling in a Leicester laboratory in 1984, handing police a new tool?

Alec Jeffreys had his 'eureka moment' on seeing an X-ray film that showed likenesses and differences in the DNA of one family. Police first used the method to catch a double murderer.

Which Chinese scientist was jailed for three years after announcing the first gene-edited babies in 2018?

He Jiankui had edited the embryos of twin girls, known as Lulu and Nana, to make them resistant to HIV. A Chinese court convicted him of illegal medical practice and fined him 3 million yuan.