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Genetics of human blood types

Human blood types

Our article on types of human blood

HUMAN BLOOD: An Introduction to Its Components and Types, Behavioral Sciences Department, Palomar College,

Genetics of human blood types

article to be written

Advanced topic

The inheritance of ABO blood types does not always follow such straightforward rules of inheritance. This can be seen when we examine the Bombay Phenotype. It is hard to predict the ABO blood type of children based on the phenotypes of their parents. This is due to the fact that a third antigen (H) on the surface of red cells can prevent the expected ABO blood type from occurring.

ABO Blood Types, Dr. Dennis O’Neil Behavioral Sciences Department, Palomar College, CA





Non-mendelian inheritance

Your previous study of genetics used Punnet squares. Easy to use and understand. But that all was based on certain assumptions. When these assumptions aren’t valid then we have non-Mendelian inheritance.

Recall the assumptions of Mendelian inheritance:

Law of segregation of genes (Mendel’s first Law), Law of independent assortment (Mendel’s second law), and the Law of dominance (Mendel’s third law)

But what happens if one allele is not completely dominant over another? What if a gene has several alleles? What if genes are not independent, but physically stuck to each other? Then Mendel’s assumptions are not valid.

The following text has been adapted from Biology (Macaw edition), Chapter 11, by Miller and Levine.

Incomplete Dominance

A cross between two four o’clock (Mirabilis jalapa) plants shows a common exception to Mendel’s principles. Some alleles are neither dominant nor recessive.

The F1 generation produced by a cross between red-flowered (RR) and white-flowered (WW) Mirabilis plants consists of pink-colored flowers (RW).

Which allele is dominant? Neither.

In incomplete dominance, the heterozygous phenotype lies some- where between the two homozygous phenotypes.

Incomplete dominance

Incomplete dominance, from Macaw Biology, Miller and Levine.



Phenotypes produced by both alleles are clearly expressed.

Example: In certain breeds of chicken, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens have a color described as “erminette,” speckled with black and white feathers.

Unlike the blending of red and white colors in heterozygous four o’clocks, black and white colors appear separately in chickens.


Many human genes, including one for a protein that controls cholesterol levels in the blood, show codominance, too. People with the heterozygous form of this gene produce two different forms of the protein, each with a different effect on cholesterol levels.

Multiple Alleles

Usually there are more than two alleles (versions of a gene.) There are multiple alleles.

Consider coat color in rabbits It is determined by a single gene that has at least four different alleles.

The four alleles display a pattern of simple dominance that can produce four coat colors.

Many other genes have multiple alleles, including the human genes for blood type.

Human blood types: examples of multiple alleles

Genetics of human blood types

Polygenic Traits

Traits controlled by two or more genes are called polygenic traits.

Example: The variety of skin color in humans comes about because many different genes control this trait.

The evolutionary genetic architecture of skin pigmentation in three populations.

The evolutionary genetic architecture of skin pigmentation in three populations. http://www.nature.com/milestones/skinbio4/full/skinbio20113a.html

Genes and the Environment

Environmental conditions can affect gene expression in many ways – this can change the traits that an organism develops (phenotype).

Example: Changes in temperature….. tba

Example: A person’s lifestyle literally causes chemical changes to control molecules on one’s DNA, and this then affects how the DNA is expressed. This is related to the subject of epigenetics.

gene environment interactions in human obesity

From The importance of gene–environment interactions in human obesity, Hudson Reddon, Jean-Louis Guéant, David Meyre, Clinical Science Aug 08, 2016, 130

Learning Standards

HS-LS3-1. Develop and use a model to show how DNA in the form of chromosomes is passed from parents to offspring through the processes of meiosis and fertilization in sexual reproduction.

HS-LS3-2. Make and defend a claim based on evidence that genetic variations (alleles) may result from (a) new genetic combinations via the processes of crossing over and random segregation of chromosomes during meiosis, (b) mutations that occur during replication, and/or (c) mutations caused by environmental factors. Recognize that mutations that occur in gametes can be passed to offspring.

HS-LS3-4(MA). Use scientific information to illustrate that many traits of individuals, and the presence of specific alleles in a population, are due to interactions of genetic factors and environmental factors.


DNA evidence offers proof of North American native population decline due to arrival of Europeans

by Bob Yirka, Phys.org

Most history books report that Native American populations in North America declined significantly after European colonizers appeared, subsequent to the “discovery” of the new world by Christopher Columbus in 1492, reducing their numbers by half or more in some cases. Most attribute this decline in population to the introduction of new diseases, primarily smallpox and warfare.

To back up such claims, historians have relied on archaeological evidence and written documents by new world settlers. Up to now however, no physical evidence has been available to nail down specifics regarding population declines, such as when they actually occurred and what caused it to occur. Now however, three researchers with various backgrounds in anthropological and genome sciences have banded together to undertake a study based on mitochondrial DNA evidence, and have found, as they report in their study published in the Proceedings of the National Academy of Sciences, that native populations in North America did indeed decline by roughly fifty percent, some five hundred years ago.

What’s perhaps most interesting in the study, is the implication that the sudden drop in population appeared to occur almost right after the arrival of Europeans, which means before settlement began. This means that the decline would have come about almost exclusively as a result of disease sweeping naturally through native communities, rather than from warfare, or mass slaughter as some have suggested and that stories of settlers using smallpox as a weapon may be exaggerated.

Also of interest is that the researchers found that the native population peaked some 5,000 years ago, and held steady, or even declined slightly, until the arrival of Europeans, and that the population decline that occurred was transient, meaning that it gradually rebounded as those Native Americans that survived the initial wave of smallpox passed on their hearty genes to the next generation.

The results of this research also seem to settle the argument of whether the massive loss of life due to disease was regional, as some historians have argued, or widespread as others have claimed; siding firmly with the latter.

In studying the DNA, of both pre-European arrival native population samples and that of their ancestors alive today, the researchers noted that those alive today are more genetically similar to one another than were their ancestors, which suggests a population decline and then resurgence, and that is how, by backtracking, they came to conclude that the decline occurred half a century ago. The authors are quick to point out however that the margin of error in their work does allow for the possibility that the population decline occurred somewhat later than their results showed and note that further research will need to be done to create a more precise timeline of events.

Native Americans experienced a strong population bottleneck coincident with European contact, Brendan D. O’Fallona and Lars Fehren-Schmitz

PNAS, Published online before print December 5, 2011, doi: 10.1073/pnas.1112563108


Americapox: The Missing Plague

By CGP Grey, an an educational YouTuber. He produces explanatory videos on science, politics, geography, economics, and history. This is a transcript of his video Americapox: The Missing Plague, www.cgpgrey.com/blog/americapox

Between the first modern Europeans arriving in 1492 and the Victorian age, the indigenous population of the new world [native American Indians] dropped by at least 90%.

Native_American_Population Plague

The cause?

Not the conquistadores and company — they killed lots of people but their death count is nothing compared to what they brought with them: small pox, typhus, tuberculosis, influenza, bubonic plague, cholera, mumps, measles and more leapt from those first explores to the costal tribes, then onward the microscopic invaders spread through a hemisphere of people with no defenses against them. Tens of millions died.

These germs decided the fate of these battles long before the fighting started.

Now ask yourself: why didn’t Europeans get sick?

If new-worlders were vulnerable to old-world diseases, then surely old-worlders would be vulnerable to new world diseases.

Yet, there was no Americapox spreading eastward infecting Europe and cutting the population from 90 million to 9. Had Americapox existed it would have rather dampened European ability for transatlantic expansion.

To answer why this didn’t happen: we need first to distinguish regular diseases — like the common cold — from what we’ll call plagues.

1) Spread quickly between people.

Sneezes spread plages faster than handshakes which are faster than… closeness. Plagues use more of this than this.

2) They kill you quickly or you become immune.

Catch a plague and your dead within seven to thirty days. Survive and you’ll never get it again. Your body has learned to fight it, you might still carry it — the plague lives in you, you can still spread it, but it can’t hurt you.

The surface answer to this question isn’t that Europeans had better immune systems to fight off new world plages — it’s that new world didn’t have plagues for them to catch. They had regular diseases but there was no Americapox to carry.

These are history’s biggest killers, and they all come from the old world.

But why?

Let’s dig deeper, and talk Cholera, a plague that spreads if your civilization does a bad job of separating drinking water from pooping water. London was terrible at this making it the cholera capital of the world. Cholera can rip through dense neighborhoods killing swaths of the population, before moving onward. But that’s the key: it has to move on.

In a small, isolated group, a plague like cholera cannot survive — it kills all available victims, leaving only the immune and then theres nowhere to go — it’s a fire that burns through its fuel.

But a city — shining city on the hill — to which rural migrants flock, where hundreds of babies are born a day: this is sanctuary for the fire of plague; fresh kindling comes to it. The plague flares and smolders and flares and smolders again — impossible to extinguish.

Historically in city borders plagues killed faster than people could breed. Cities grew because more people moved to them than died inside of them. Cities only started growing from their own population in the 1900s when medicine finally left its leaches and bloodletting phase and entered its soap and soup phase — giving humans some tools to slow death.

But before that a city was an unintentional playground for plages and a grim machine to sort the immune from the rest.

So the deeper, answer is that The New World didn’t have plagues because the new world didn’t have big, dense, terribly sanitized deeply interconnected cities for plages to thrive.

OK, but The New World wasn’t completely barren of cities. And tribes weren’t completely isolated, otherwise the newly-arrived smallpox in the 1400s couldn’t have spread.

Cities are only part of the puzzle: they’re required for plages, but cities don’t make the germs that start the plagues — those germs come from the missing piece.

Now, most germs don’t want to kill you for the same reason you don’t want to burn down your house: germs live in you. Chromic diseases like leprosy are terrible because they’re very good at not killing you.

Plague lethality is an accident, a misunderstanding, because the germs that cause them don’t know they’re in humans, they’re germs that think they’re in this.

Plagues come from animals.

Whooping cough comes from pigs, and does flu as well as from birds. Our friend the cow alone is responsible for measles, tuberculosis, and smallpox.

For the cow these diseases are no big deal — like colds for us. But when cow germs get in humans thing things they do to make the cow a little sick, makes humans very sick. Deadly sick.

Germs jumping species like this is extraordinarily rare. That’s why generations of humans can spend time around animals just fine. Being the patient zero of a new animal-to-human plague is winning a terrible lottery.

But a colonial-age city raises the odds: there used to be animals everywhere, horses, herds of livestock in the streets, open slaughterhouses, meat markets pre-refrigeration, and a river of literal human and animal excrement running through it all.

A more perfect environment for diseases to jump species could hardly be imagined.

So the deeper answer is that plagues come from animals, but so rarely you have to raise the odds and with many chances for infection and give the new-born plague a fertile environment to grow. The old world had the necessary pieces in abundance.

But, why was a city like London filled with sheep and pigs and cows and Tenochtitlan wasn’t?

This brings us to the final level. (For this video anyway)

Some animals can be put to human use — this is what domestication means, animals you can breed, not just hunt.

Forget a the moment the modern world: go back to 10,000BC when tribes of humans reached just about everywhere. If you were in one of these tribes what local animals could you capture, alive, and successfully pen to breed?

Maybe you’re in North Dakota and thinking about catching a Buffalo: an unpredictable, violent tank on hooves, that can outrun you across the planes, leap over your head head and travels in herds thousands strong.

Oh, and you have no horses to help you — because there are no horses on the continent. Horses live here — and won’t be brought over until, too late.

It’s just you, a couple buddies, and stone-based tools. American Indians didn’t fail to domesticate buffalo because they couldn’t figure it out. They failed because it’s a buffalo. No one could do it — buffalo would have been amazing creature to put to human work back in BC, but it’s not going to happen — humans have only barely domesticated buffalo with all our modern tools.

The New World didn’t have good animal candidates for domestication. Almost everything big enough to be useful is also was to too dangerous, or too agile.

Meanwhile the fertile crescent to central Europe had: cows and and pigs and sheep and goats, easy pests animals comparatively begging to be domesticated.

A wild boar is something to contend with if you only have stone tools but it’s possible to catch and pen and bread and feed to eat — because pigs can’t leap to the sky or crush all resistance beneath their hooves.

In The New World the only native domestication contestant was: llamas. They’re better than nothing, which is probably why the biggest cities existed in South America — but they’re no cow. Ever try to manage a heard of llamas in the mountains of Peru? Yeah, you can do it, but it’s not fun. Nothing but drama, these llamas.

These might seem, cherry-picked examples, because aren’t there hundreds of thousands of species of animals? Yes, but when you’re stuck at the bottom of the tech tree almost none of them can be domesticated. From the dawn of man until this fateful meeting humans domesticated maybe a baker’s dozen of unique species the world over, and even to get that high a number you need to stretch it to include honeybees and silkworms. Nice to have, but you can’t build a civilization on a foundation of honey alone.

These early tribes weren’t smarter, or better at domestication. The old world had more valuable and easy animals. With dogs, herding sheep and cattle is easier. Now humans have a buddy to keep an eye on the clothing factory, and the milk and cheeseburger machine, and the plow-puller. Now farming is easier, which means there’s more benefit to staying put, which means more domestication, which means more food which means more people and more density and oh look where we’re going. Citiesville, population lots, bring your animals, plagues welcome.

That is the full answer: The lack of new world animals to domesticate, limited not only exposure to germs sources but also limited food production, which limited population growth, which limited cities, which made plagues in The New World an almost impossibility. In the old, exactly the reverse. And thus a continent full of plague and a continent devoid of it.

So when ships landed in the new world there was no Americapox to bring back.

The game of civilization has nothing to do with the players, and everything to do with the map. Access to domesticated animals in numbers and diversity, is the key resource to bootstrapping a complex society from nothing — and that complexity brings with it, unintentionally, a passive biological weaponry devastating to outsiders.

Start the game again but move the domesticable animals across the sea and history’s arrow of disease and death flows in the opposite direction.


Don’t Blame Columbus for All the Indians’ Ills

By JOHN NOBLE WILFORD, OCT. 29, 2002, The New York Times

Europeans first came to the Western Hemisphere armed with guns, the cross and, unknowingly, pathogens. Against the alien agents of disease, the indigenous people never had a chance. Their immune systems were unprepared to fight smallpox and measles, malaria and yellow fever.

The epidemics that resulted have been well documented. What had not been clearly recognized until now, though, is that the general health of Native Americans had apparently been deteriorating for centuries before 1492.

That is the conclusion of a team of anthropologists, economists and paleopathologists who have completed a wide-ranging study of the health of people living in the Western Hemisphere in the last 7,000 years.

The researchers, whose work is regarded as the most comprehensive yet, say their findings in no way diminish the dreadful impact Old World diseases had on the people of the New World. But it suggests that the New World was hardly a healthful Eden.

More than 12,500 skeletons from 65 sites in North and South America — slightly more than half of them from pre-Columbians — were analyzed for evidence of infections, malnutrition and other health problems in various social and geographical settings.

The researchers used standardized criteria to rate the incidence and degree of these health factors by time and geography. Some trends leapt out from the resulting index. The healthiest sites for Native Americans were typically the oldest sites, predating Columbus by more than 1,000 years. Then came a marked decline.

”Our research shows that health was on a downward trajectory long before Columbus arrived,” Dr. Richard H. Steckel and Dr. Jerome C. Rose, study leaders, wrote in ”The Backbone of History: Health and Nutrition in the Western Hemisphere,” a book they edited. It was published in August.

Dr. Steckel, an economist and anthropologist at Ohio State University, and Dr. Rose, an anthropologist at the University of Arkansas, stressed in interviews that their findings in no way mitigated the responsibility of Europeans as bearers of disease devastating to native societies. Yet the research, they said, should correct a widely held misperception that the New World was virtually free of disease before 1492.

In an epilogue to the book, Dr. Philip D. Curtin, an emeritus professor of history at Johns Hopkins University, said the skeletal evidence of the physical well-being of pre-Columbians ”shows conclusively that however much it may have deteriorated on contact with the outer world, it was far from paradisiacal before the Europeans and Africans arrived.”

About 50 scientists and scholars joined in the research and contributed chapters to the book. One of them, Dr. George J. Armelagos of Emory University, a pioneer in the field of paleopathology, said in an interview that the research provided an ”evolutionary history of disease in the New World.”

The surprise, Dr. Armelagos said, was not the evidence of many infectious diseases, but that the pre-Columbians were not better nourished and in general healthier.

Others said the research, supported by the National Science Foundation and Ohio State, would be the talk of scholarly seminars for years to come and the foundation for more detailed investigations of pre-Columbian health. Dr. Steckel is considering conducting a similar study of health patterns well into European prehistory.

”Although some of the authors occasionally appear to overstate the strength of the case they can make, they are also careful to indicate the limitations of the evidence,” Dr. Curtin wrote of the Steckel-Rose research. ”They recognize that skeletal material is the best comparative evidence we have for the human condition over such a long period of time, but it is not perfect.”

The research team gathered evidence on seven basic indicators of chronic physical conditions that can be detected in skeletons — namely, degenerative joint disease, dental health, stature, anemia, arrested tissue development, infections and trauma from injuries. Dr. Steckel and Dr. Rose called this ”by far the largest comparable data set of this type ever created.”

The researchers attributed the widespread decline in health in large part to the rise of agriculture and urban living. People in South and Central America began domesticating crops more than 5,000 years ago, and the rise of cities there began more than 2,000 years ago.

These were mixed blessings. Farming tended to limit the diversity of diets, and the congestion of towns and cities contributed to the rapid spread of disease. In the widening inequalities of urban societies, hard work on low-protein diets left most people vulnerable to illness and early death.

Similar signs of deleterious health effects have been found in the ancient Middle East, where agriculture started some 10,000 years ago. But the health consequences of farming and urbanism, Dr. Rose said, appeared to have been more abrupt in the New World.

The more mobile, less densely settled populations were usually the healthiest pre-Columbians. They were taller and had fewer signs of infectious lesions in their bones than residents of large settlements. Their diet was sufficiently rich and varied, the researchers said, for them to largely avoid the symptoms of childhood deprivation, like stunting and anemia. Even so, in the simplest hunter-gatherer societies, few people survived past age 50. In the healthiest cultures in the 1,000 years before Columbus, a life span of no more than 35 years might be usual.

In examining the skeletal evidence, paleopathologists rated the healthiest pre-Columbians to be people living 1,200 years ago on the coast of Brazil, where they had access to ample food from land and sea. Their relative isolation protected them from most infectious diseases.

Conditions also must have been salubrious along the coasts of South Carolina and Southern California, as well as among the farming and hunting societies in what is now the Midwest. Indian groups occupied the top 14 spots of the health index, and 11 of these sites predate the arrival of Europeans.

The least healthy people in the study were from the urban cultures of Mexico and Central America, notably where the Maya civilization flourished presumably at great cost to life and limb, and the Zuni of New Mexico. The Zuni lived at a 400-year-old site, Hawikku, a crowded, drought-prone farming pueblo that presumably met its demise before European settlers made contact.

It was their hard lot, Dr. Rose said, to be farmers ”on the boundaries of sustainable environments.”

”Pre-Columbian populations were among the healthiest and the least healthy in our sample,” Dr. Steckel and Dr. Rose said. ”While pre-Columbian natives may have lived in a disease environment substantially different from that in other parts of the globe, the original inhabitants also brought with them, or evolved with, enough pathogens to create chronic conditions of ill health under conditions of systematic agriculture and urban living.”

In recent examinations of 1,000-year-old Peruvian mummies, for example, paleopathologists discovered clear traces of tuberculosis in their lungs, more evidence that native Americans might already have been infected with some of the diseases that were thought to have been brought to the New World by European explorers.

Tuberculosis bears another message: as an opportunistic disease, it strikes when times are tough, often overwhelming the bodies of people already weakened by malnutrition, poor sanitation in urban centers and debilitated immune systems.

The Steckel-Rose research extended the survey to the health consequences of the first contacts with American Indians by Europeans and Africans and the health of European-Americans and African-Americans up to the early 20th century.

Not surprisingly, African-American slaves were near the bottom of the health index. An examination of plantation slaves buried in South Carolina, Dr. Steckel said, revealed that their poor health compared to that of ”pre-Columbian Indian populations threatened with extinction.”

On the other hand, blacks buried at Philadelphia’s African Church in the 1800’s were in the top half of the health index. Their general conditions were apparently superior to those of small-town, middle-class whites, Dr. Steckel said.

The researchers found one exception to the rule that the healthiest sites for Native Americans were the oldest sites. Equestrian nomads of the Great Plains of North America in the 19th century seemed to enjoy excellent health, near the top of the index. They were not fenced in to farms or cities.

In a concluding chapter of their book, Dr. Steckel and Dr. Rose said the study showed that ”the health decline was precipitous with the changes in ecological environments where people lived.” It is not a new idea in anthropology, they conceded, ”but scholars in general have yet to absorb it.”


Related articles

The Great Dying 1616-1619, Ipswich Historical Commission


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Peptide bonds – How we make proteins

2 amino acids can join to form a peptide.

A very long peptide is known as a protein.

When they join one of the amino acid’s loses an H atom, while the other loses an OH moiety (part of a molecule)  They join together to form H2O (water.) This is a condensation reaction.

peptide bond formation 1

Doc Kaiser’s Microbiology Home Page (Gary E. Kaiser)


Here is another animation of the same process

The CONH link created is called a peptide bond (red)
Water (blue) is removed.

This process can be continued repeatedly to form longer peptides (eventually, when they are over 50 amino acids long, we call them proteins.)

peptide bond formation 2

BioTopics.co.uk by Richard Steane

The monomer here is an amino acid.

The polymer here is a peptide or protein.

These are 20 different types of common amino acids.

Amino acids are bonded together to make peptides, or proteins.

A peptide is just a small protein, less than 50 amino acids (aa) long.

Proteins are much larger, 100 aa, 500 aa, even 1,000 aa.

A chain of amino acids folds up into a shape.

Every protein has its own shape.


Teaching protein translation

Teaching how DNA gets turned into mRNA, and then hooks up to tRNA with amino acids, and forms proteins. It’s not easy for everyone, and especially difficult for many ELL and SPED students. Solution? Make it tactile – use manipulatives. I use a large student table as a cell, and pieces on the table represent organelles and molecules.

I spent a long time finding the right graphics to represent the nucleus, chromosomes, DNA, RNA, mitochondria, and of course the rough ER and Golgi (I always try and reinforce the idea that cells are simultaneously full of many organelles, even if we’re only using a few of them.)

Then I printed them out on heavy stock paper. (I need to laminate it next time, but this was a trial run.) Cut out all the pieces.

The trick is to have many nucleotides, so they can get practice with multiple combinations. Here 27 bases, for 9 codons, making an 8 amino acid peptide (plus one STOP codon.)

Here is the PDF file with the graphics (DNA to mRNA to ribosome to tRNA)

And here is what it looks like on a table top, when students use them.

DNA protein translation manipulative

DNA protein translation manipulative 2

Learning Standards

HS-LS1-1. Construct a model of transcription and translation to explain the roles of DNA and RNA that code for proteins that regulate and carry out essential functions of life.


Michelangelo’s Secret Message in the Sistine Chapel

Michelangelo’s Secret Message in the Sistine Chapel: A Juxtaposition of God and the Human Brain

Scientific American, R. Douglas Fields on May 27, 2010

At the age of 17 he began dissecting corpses from the church graveyard. Between the years 1508 and 1512 he painted the ceiling of the Sistine Chapel in Rome. Michelangelo Buonarroti—known by his first name the world over as the singular artistic genius, sculptor and architect—was also an anatomist, a secret he concealed by destroying almost all of his anatomical sketches and notes. Now, 500 years after he drew them, his hidden anatomical illustrations have been found—painted on the ceiling of the Sistine Chapel, cleverly concealed from the eyes of Pope Julius II and countless religious worshipers, historians, and art lovers for centuries—inside the body of God.

Michelangelo Light Darkness First_Day_of_Creation

This is the conclusion of Ian Suk and Rafael Tamargo, in their paper in the May 2010 issue of the scientific journal Neurosurgery. Suk and Tamargo are experts in neuroanatomy at the Johns Hopkins University School of Medicine in Baltimore, Maryland.

In 1990, physician Frank Meshberger published a paper in the Journal of the American Medical Association deciphering Michelangelo’s imagery with the stunning recognition that the depiction in God Creating Adam in the central panel on the ceiling was a perfect anatomical illustration of the human brain in cross section. Meshberger speculates that Michelangelo surrounded God with a shroud representing the human brain to suggest that God was endowing Adam not only with life, but also with supreme human intelligence.

Now in another panel The Separation of Light from Darkness, Suk and Tamargo have found more. Leading up the center of God’s chest and forming his throat, the researchers have found a precise depiction of the human spinal cord and brain stem.

Michelangelo 1

Is the ceiling of the Sistine Chapel a 500 year-old puzzle that is only now beginning to be solved? What was Michelangelo saying by construction the voice box of God out of the brain stem of man? Is it a sacrilege or homage?

It took Michelangelo four years to complete the ceiling of the Sistine Chapel. He proceeded from east to west, starting from the entrance of the Chapel to finish above the altar. The last panel he painted depicts God separating light from darkness. This is where the researchers report that Michelangelo hid the human brain stem, eyes and optic nerve of man inside the figure of God directly above the altar.

Art critics and historians have long puzzled over the odd anatomical irregularities in Michelangelo’s depiction of God’s neck in this panel, and by the discordant lighting in the region. The figures in the fresco are illuminated diagonally from the lower left, but God’s neck, highlighted as if in a spotlight, is illuminated straight-on and slightly from the right.

Michelangelo 2

How does one reconcile such clumsiness by the world’s master of human anatomy and skilled portrayer of light with bungling the image of God above the altar? Suk and Tamargo propose that the hideous goiter-disfigured neck of God is not a mistake, but rather a hidden message. They argue that nowhere else in any of the other figures did Michelangelo foul up his anatomically correct rendering of the human neck.

They show that if one superimposes a detail of God’s odd lumpy neck in the Separation of Light and Darkness on a photograph of the human brain as seen from below, the lines of God’s neck trace precisely the features of the human brain [see images at right].

There is something else odd about this picture. A role of fabric extends up the center of God’s robe in a peculiar manner. The clothing is bunched up here as is seen nowhere else, and the fold clashes with what would be the natural drape of fabric over God’s torso. In fact, they observe, it is the human spinal cord, ascending to the brain stem in God’s neck. At God’s waist, the robe twists again in a peculiar crumpled manner, revealing the optic nerves from two eyes, precisely as Leonardo Da Vinci had shown them in his illustration of 1487. Da Vinci and Michelangelo were contemporaries and acquainted with each other’s work.

The mystery is whether these neuroanatomical features are hidden messages or whether the Sistine Chapel a Rorshach tests upon which anyone can extract an image that is meaningful to themselves. The authors of the paper are, after all, neuroanatomists. The neuroanatomy they see on the ceiling may be nothing more than the man on the moon.
But Michelangelo also depicted other anatomical features elsewhere in the ceiling, according to other scholars; notably the kidney, which was familiar to Michelangelo and was of special interest to him as he suffered from kidney stones.

If the hidden figures are intentional, what do they mean? The authors resist speculation, but a great artist does not merely reproduce an object in a work of art, he or she evokes meaning through symbolism. Is Separation of Light from Darkness an artistic comment on the enduring clash between science and religion?

Recall that this was the age when the monk Copernicus was denounced by the Church for theorizing that the Earth revolved around the sun. It was a period of struggle between scientific observation and the authority of the Church, and a time of intense conflict between Protestants and Catholics.

It is no secret that Michelangelo’s relationship with the Catholic Church became strained. The artist was a simple man, but he grew to detest the opulence and corruption of the Church. In two places in the masterpiece, Michelangelo left self portraits—both of them depicting himself in torture. He gave his own face to Saint Bartholomew’s body martyred by being skinned alive, and to the severed head of Holofernes, who was seduced and beheaded by Judith.

Michelangelo was a devout person, but later in life he developed a belief in Spiritualism, for which he was condemned by Pope Paul IV. The fundamental tenet of Spiritualism is that the path to God can be found not exclusively through the Church, but through direct communication with God. Pope Paul IV interpreted Michelangelo’s Last Judgment, painted on the wall of the Sistine Chapel 20 years after completing the ceiling, as defaming the church by suggesting that Jesus and those around him communicated with God directly without need of Church. He suspended Michelangelo’s pension and had fig leaves painted over the nudes in the fresco. According to the artist’s wishes, Michelangelo’s body is not buried on the grounds of the Vatican, but is instead interred in a tomb in Florence.

Perhaps the meaning in the Sistine Chapel is not of God giving intelligence to Adam, but rather that intelligence and observation and the bodily organ that makes them possible lead without the necessity of Church directly to God. The material is rich for speculation and the new findings will doubtlessly spark endless interpretation. We may never know the truth, but in Separation of Light from Darkness, Michelangelo’s masterpiece combines the worlds of art, religion, science, and faith in a provocative and awe inspiring work of art, which may also be a mirror.

Images from “Concealed Neuroanatomy in Michelangelo’s Separation of Light From Darkness in the Sistine Chapel,” by Ian Suk and Rafael J. Tamargo in Neurosurgery, Vol. 66, No. 5, pp. 851-861.

About the author: R. Douglas Fields, Ph.D., is a neuroscientist and an adjunct professor at the University of Maryland, College Park. He is author of Why We Snap, about the neuroscience of sudden aggression, and The Other Brain, about glia. Fields serves on Scientific American Mind’s board of advisers.


Related articles

Separation of Light from Darkness. Article on the painting from Wikipedia.


Origami membrane protein

All cell membranes have proteins embedded in them. Each protein has its own job.

Students may draw them like this:

But a more sophisticated artist could show much more detail.

One could show that proteins are three-dimensional machines, with movable parts.

Creative Biomart Lipidsome-Based-Membrane-Protein-Production

Now instead of a static image, visualize how busy it is near the cell membrane:

Many molecules going in and out of a cell – and not randomly.

Membrane proteins open or close, as needed, to let certain molecules in, and other ones out.

Cell membrane lipid bilayer animation

What we’re going to see today is a student in our class build a three dimensional model of a membrane protein.

He made one monomer; and then attached several of them to make a polymer.

Monomer Polymer Lego analogy

Instead of attaching eight monomers in a straight line, he’ll form them into a circle:

This becomes a model of a protein that floats in a cell’s membrane,

It can have two shapes, closed or opened, depending on how it’s folded.

It allows certain molecules in or out of a cell, as needed.

protein folding 1

protein folding 2

protein folding 3

protein folding 4

protein folding 5

protein folding 6

protein folding 7

For instructions we may refer to a video from AskABiologist:

Proteins are made of building blocks called amino acids, and have their own special shape. Not only do they look different, but they have different jobs to do inside the cell. Some proteins help move things around in the body, others act like support structures or glue to hold parts of the cell together, and some can help reactions in the cell go faster. The protein we’re making is a channel that sits in the outer cell surface, or membrane, and works like a door that lets certain molecules pass through. Some channels are open all the time while others can be closed depending on signals from the cell or the environment.

Narration by Rebecca Elaine Ryan
Original origami design by Florence Temko

Step-by-step directions

Here’s the video from AskABiologist


Learning Standards

Massachusetts Curriculum Frameworks: Biology

8.MS-PS1-1. Develop a model to describe that (a) atoms combine in a multitude of ways to
produce pure substances which make up all of the living and nonliving things that we
encounter, (b) atoms form molecules and compounds that range in size from two to
thousands of atoms, and (c) mixtures are composed of different proportions of pure

Clarification Statement: Examples of molecular-level models could include drawings, three-dimensional ball and stick structures, and computer representations showing different molecules with different types of atoms.

HS-LS1-6. Construct an explanation based on evidence that organic molecules are primarily composed of six elements, where carbon, hydrogen, and oxygen atoms may combine with nitrogen, sulfur, and phosphorus to form monomers that can further combine to form large carbon-based macromolecules.
Clarification Statements:
• Monomers include amino acids, mono- and disaccharides, nucleotides, and fatty acids.
• Organic macromolecules include proteins, carbohydrates (polysaccharides), nucleic acids, and lipids.

Disciplinary Core Idea Progression Matrix: PS1.A Structure of matter: That matter is composed of atoms and molecules can be used to explain the properties of substances, diversity of materials, how mixtures will interact, states of matter, phase changes, and conservation of matter.