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Felix Hoppe-Seyler

By Elof Axel Carlson

Elof Axel Carlson

I enjoy doing history of science because I learn so much when delving into the past. If I am reading about cell theory and the types of tissues there are, I remember the course in microscopic techniques I took as an undergraduate at NYU.

I did not know then that the microtome to cut slices of tissue for making slides was first introduced by Johannes Purkinje. I did not know that growing bacteria on agar plates or slants in test tubes to obtain pure cultures was first done by Robert Koch. I did not know that the word “mutation,” as a change in heredity, was first introduced by Hugo de Vries. Similarly, I did not know that Bernhard Tollens first showed carbohydrates were composed of sugars.

It was William Cheselden who first demonstrated that the role of saliva was to break down food for digestion. I did not know the chemical notation for representing molecules, like CO2 being carbon dioxide was invented by Jöns Berzelius. I did not know the first person to show that oxygen binds to hemoglobin was Felix Hoppe-Seyler. But I did know that Albrecht Kossel was the first to isolate and name the nitrogenous biases of nucleic acid and he called them adenine, guanine, thymine, cytosine and uracil. 

I did not know ringworm was shown to be a fungal parasite by Johann Schönlein. He also changed the name “consumption” to “tuberculosis” and made a third contribution: He was the first science professor to teach in his native tongue, German, instead of Latin to his students. It was Rudolf Leuckart who worked out the nematode parasite causing trichinosis in pork, and his work led to compulsory meat inspection in most industrial countries. The first phylogenetic tree for evolutionary history of plants or animals was constructed by Ernst Haeckel (that I did know).

Even the nouns I use as a scientist have known origins: Tissue was first introduced by Marie François Xavier Bichat at the time of the French Revolution (his 20 different tissues became the four basic tissues I learned as an undergraduate).

The cell theory was first promoted by Matthias Schleiden and Theodor Schwann in 1838. It was changed to a cell doctrine (all cells arise from preceding cells) by Robert Remak and Rudolf Virchow. Most of the names I have mentioned lived in the 1700s and 1800s. We remember the names of 20th century scientists partly because they are published in textbooks. But if one studies a field and looks at old textbooks of about 100 years ago or more, lots of terms used in those past generations have disappeared. Also, the names of then recent scientists are abundant.

It is a curious honor to be a discoverer of something important and then 100 years after your death your role in it is no longer present in texts or scientific articles. Who remembers that Karl Gegenbaur first introduced the idea of homology into comparative anatomy (your hands, a bat’s wings and a horse’s forefeet are homologous because they have an embryonic common formation from an initial limb bud)?   

Scientists do science because they enjoy the opportunity to make discoveries. Very few will be remembered for centuries like Galileo, Newton or Darwin. All who have published will be dug up centuries from now by historians curious about the origins of ideas and processes of our own generation.

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

By Elof Axel Carlson

Elof Axel Carlson

Science is a way of knowing based on reason. That aspect of science would also apply to logic or the creation of mathematical fields. But when science is applied to the material world, reason is not sufficient. Modern science includes the use of data from observations and from the use of tools to produce data. A third aspect of science is characteristic of modern science. It is the design of experiments that predict what type of data will be found. 

Science differs from revelation, tradition, authority or religious belief because these nonscientific ways that culture forms often require faith or do not attempt to apply science to their beliefs. This difference in interpreting the world around us allowed scientists to be skeptical, to require evidence and to apply more testing and tools to expand the applications of science to the universe and to life.  

This resulted in many new fields of science. Astronomers purged themselves of astrology. Chemists purged themselves of alchemy. Medicine purged itself of quackery. All sciences rejected magic (except as entertainment) and wishful thinking. 

Modern science arose in Italy in the 1500s.  We attribute to Galileo the origins of modern physics and astronomy. He worked out physical laws for falling bodies or bodies rolling down inclined planes. He introduced the mathematical equations to describe and to predict the time required and the distances involved in projectiles dropped, thrown or shot from cannons. He used the telescope he constructed to detect moons around Jupiter, phases of Venus, Saturn’s rings (they looked like ears to him) and mountains and craters on the moon. 

Modern science arose in Italy because the first universities arose in Italy (the University of Bologna was the first in 1088). The Renaissance began in Italy with increased members of the middle class, formation of large cities, importing of knowledge from trade with Asia and Africa and an accumulation of wealth that was spent on architecture, the arts, hobbies, scholarship and curiosity for those with leisure time. 

Artists like Albrecht Dürer went from Bavaria to Italy to study anatomy. William Harvey went from England to study medicine in Italy (Galileo was on the faculty when Harvey was a student) and brought back experimentation to the human body and the circulation of blood.  

German universities benefited from sending students to Italy. In turn the Italian-trained German professors brought their skills to France. During the Enlightenment, French science flourished with Lavoisier in chemistry and Cuvier in biology. From France, science moved to the United States and the founding president of Johns Hopkins University, Daniel Coit Gilman, went to Europe and designed the American University model for its doctorate. 

For the life sciences he recruited a student of Thomas Huxley’s, H. Newell Martin, and W. K. Brooks, one of the first American students of Louis Agassiz (famed for demonstrating and naming the Ice Age that covered large parts of Europe and North America). Martin and Brooks mentored T. H. Morgan. Morgan, at Columbia University, mentored H. J. Muller; and Muller, at Indiana University, mentored me. 

While where a student goes for a doctorate may vary with time, over the past 500 years, the three features of science – reason, data collection and experimentation have not changed. Instead, they have provided enormous applications to our lives from computers to public health, to air flight, to transcontinental roads and railways. They have extended our life expectancy by more than 50 years since the Renaissance began. They allowed humans to walk on the moon and determine how many children to have and when to have them; and they allow us to eat fresh fruits and vegetables all year round. 

Science has its limitations. It cannot design ideal governments, what values to live by, what purpose we choose for motivating us or supply the yearnings of wishful thinking (we will never be rid of all accidents, all diseases, or live forever). It co-exists with the humanities and the arts in filling out each generation’s expectations.   

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

Penguins are among the few animals that live in the South Pole. Stock photo

By Elof Axel Carlson

Elof Axel Carlson

Life abounds from pole to pole and from the bottom of oceans to the peaks of Asian mountain tops. It does this by using the air, water and land to sustain life.

For most of the time on Earth life was confined to single-celled organisms, mostly bacteria. They take in water across a cell membrane. Most do not use oxygen from the air. Those that do came later, when some bacteria developed tools to use sunlight to combine carbon dioxide in the air with water to produce food (carbohydrates) and more abundant energy for the cell. They released oxygen and the atmosphere began to accumulate oxygen. 

Most forms of multicellular life use oxygen from the air to provide the energy to sustain their cellular life. Multicellularity permitted specialization of cells to form tissues, and the tissues then permitted organs to specialize in exchanging carbon dioxide (a waste product for animals) for oxygen.

The branching of limbs on trees is efficient to increase surfaced area for gaseous exchanges. So too are the branching of filaments in the gills of fish or the trachea of insects or the branching of the bronchi in our lungs.

When I see a tree, I see those organ systems reaching skyward with terminal leaves and an equally branched underground of roots, which are bringing in water and minerals from the land into which they are penetrated. The artist sees the beauty of the landscape. The mystic feels the awe of the complexity that seems beyond human comprehension. The scientist explores the structures and assigns functions as they emerge through the tools of science and experimentation.

It is as thrilling to me to see the cellular network of living tissues or organs under a microscope as it is to watch the changing scenery of life when driving from Indiana to New York, or taking walks in Amsterdam, Capetown, Samara, the Seychelles, the nature preserves in Kenya or the beaches of Baja Mexico.

I think of life through time as a fractal drawing with many repetitions creating new patterns. All of life requires a few basic activities. Life requires molecules to form membranes. It requires carbon-based compounds to produce the organelles that compose a cell.  All life (except viruses) is cellular. Life requires molecules that can store information to provide the molecules of life — proteins, nucleic acids, carbohydrates and lipids.

I think of the tools of the artist — a palette, brushes, tubes of oil paint, a canvas stretched on a frame, an easel to hold it. The artist can meticulously render a face, a still life or a landscape with the skills of many hundreds of hours of practice. 

Life also uses cellular tools to construct more complex membranes, organelles, chromosomes and vesicles to a symphony of functioning parts. Science enriches our understanding, opens new worlds of the very small and the very large that we do not normally see.  At most, a galaxy other than our own Milky Way is a mere dot in the sky, but close up it has 100 billion stars in it, most of them like our own sun. Our universe has billions of galaxies. 

As I type a page for an article or book, I am aware that I am coordinating the 37 trillion cells composing me. Human life mimics the universe in its immensity as our Earth now contains some 7 billion people. But this is humbled by the immensity of the astronomer’s universe or the biologist’s inventory of our own cells.    

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

By Elof Axel Carlson

Elof Axel Carlson

The first time I heard DNA enter popular culture was hearing a record played by my son Anders. I heard the refrain, “Hey hey, hey hey! It’s DNA that made me that way.” Anders told me it was from a song called “Sheer Heart Attack” by the rock band Queen (1977).  

Since then that idea has spread from teenage rock fans to the public sphere, and in its modified form, I hear “It’s in my DNA” when a person feels passionately about an idea. Metaphors are part of how we speak but they are not always scientifically accurate. Before the era of DNA (that began with the publishing of the double helix model of DNA in 1953 by James Watson and Francis Crick), a different set of metaphors were in use going back to antiquity. 

Intense belief or fixed behaviors have been attributed to the intestines (I feel it in my gut), to the heart (I offer my heart-felt thanks), to the skeletal system (I feel it to the marrow of my bones), to the blood (royalty are blue bloods and a psychopath’s behavior reflects bad blood) and to the nervous system (argumentative personalities are called “hot headed”). 

Sumerians studied the shape of animal guts and livers to predict the future (haruspicy). Until the Renaissance the brain was thought to be the place where blood is cooled (hence the hot-headed belief). Thoreau was described by one contemporary as sucking the marrow out of life; and blood was considered the vital fluid of life. In the Renaissance the first human blood transfusions were given to provide youthful vigor by old men who believed in rejuvenation.  

When people say, “It’s in my DNA” for a behavior, they are conveying a deeply held belief that it is part of their personality as far back as they can remember or that it is innate. But the evidence for innate human social behaviors is often lacking. There are single gene effects of the nervous system that are well documented such as Huntington’s disease, which leads to dementia and paralysis with an onset usually in middle age. 

There are also family histories of psychosis and learning difficulties. The fragile X syndrome is one such well-documented condition that leads to low intelligence. But human social traits have lots of inputs from parents, siblings, playmates, neighborhoods, regional culture, ethnicity and national identity.  

Children growing up in poverty have different expectations than children whose parents are well off and send them to elite schools. Each generation uses, as best as it can, what it knows. Our knowledge of many important aspects of life and behavior is incomplete. Hence, we keep modifying our interpretations of how life works.  

Much of what is called evolutionary psychology or genetic determinism will be modified or abandoned in years to come as we learn how our genes use memories and other acquired knowledge to shape our personalities. For many cellular processes we know the flow of information from DNA (genes) to cell organelles to cellular function to tissue formation and to organ formation.  

That detailed interpretation of human behavior is not possible now for social traits. I would love to say, “It’s in my DNA” to write these Life Line columns, but my conscience would remind me that it is based on Freudian “wish fulfillment” and not careful experimentation down to the molecular level.

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

By Elof Axel Carlson

Elof Axel Carlson

Occasionally, I read an item on Facebook that engages my attention. One item asked several celebrities (like successful billionaires) to list the five books they most enjoyed reading and briefly tell why they were important. Here are my five favorite books: 

‘Civilization and Its Discontents’ by  Sigmund Freud

Freud introduces the source of the tensions between creativity and destructiveness. He assigns it to the id/superego conflict. I would use instead our capacity for love, empathy and sympathy versus our capacity for hate, bigotry and violence. Freud calls the process sublimation. He began writing this book in 1929 and published it two years later. He predicted that the rise of Nazism was imminent and would lead to massive death because humanity does not know how to sublimate its discontents into the path of the joys of civilization — its arts, humanity, play and immense scholarship.  

‘Jean Barois’ by  Roger Martin du Gard

This is my favorite novel. It is the story of a young French boy raised by a devout Catholic family who thinks he will become a priest. He discovers instead that the more he learns the more doubts arise not only about his calling but his faith. He teaches biology and is fired for teaching evolution. His wife and daughter separate from him. He throws himself into the Freethinkers movement in France and gets involved in the Dreyfus case. He discovers that reason alone cannot sustain his life but returning to his faith is equally inadequate.  

‘The Essays of Michel de Montaigne’

Montaigne’s essays describe his life and the times in which he lived in the context of a rich appreciation of classical literature. He tries to make sense of a world that is pretentious, at war with itself and filled with irony, contradictions and lessons we can extract from the past. Read a 20th-century translation of these essays rather than the 16th-century English translation. Start with his essay on friendship and his essay: “How by various means we all end at the same place.”   

‘The Diary of Samuel Pepys’

I loved reading Pepys’s diaries and was thrilled that he was an eyewitness to the bubonic plague that swept through England in 1665 and the London fire that destroyed most of the city in 1666. Pepys is an imperfect person — not immune to accepting sacks of gold for awarding contracts for the British Navy, flirting with other women but loving his wife and learning to avoid threats to his career from others drawn to the politics of the time.

‘The Origin of Species’ by Charles Darwin 

Darwin is an excellent observer and narrator. He wrote this book as an abstract of a huge multivolume plan for presenting his theory of evolution of species by natural selection. He is careful to distinguish evidence from theory and uses the facts to derive his interpretations of how evolution works. Darwin did not start with a theory and then seek facts to support it. He went with no idea about evolution and instead allowed the hundreds of observations and findings guide him to the only interpretation that made sense of the relations he found whether it was the work of hobbyists and breeders creating new varieties of plants and animals, the geographic distribution of plants and animals he encountered in his trip around the world, or the fossils he encountered.  

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I have learned to sublimate my discontents and have had 14 books published for which I thank Freud. I find Jean Barois to be the finest writing on the conflict between science and belief, science and politics and the difficulty of finding a life that sustains us. Montaigne taught me that in difficult times, we can find many things to avoid and how diverse the world is for each new generation that emerges. I have kept a diary (now 112 volumes) more years than not since I first read Pepys’s diary in 1949. Darwin’s book taught me how to use a Baconian approach to science, letting the data amass and allowing an unbiased mind to connect the dots that make new findings and interpretations possible. 

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

Giovanni Alfonso Borelli

By Elof Axel Carlson

Elof Axel Carlson

Scientists have a tradition of citing those whose work helped shape their own ideas and experiments. Almost every scientific paper has a list of such journal articles or books cited by the authors of a published article in a peer-reviewed journal. Usually these references are to recent work that the author or authors have read. 

But one could chase back the references of each cited article and keep doing this to work that was published in the 1600s. Before that things get more complicated because science as we know it dates to the Renaissance. Most of those cited names are forgotten to us and we are taught the names of only a few of these many scientists. 

Thus, we single out the major contributors like Galileo and his work supporting the Copernican theory that Earth and other planets move around the sun. We cite Vesalius’s work on human anatomy, the first accurate depiction of the organs of the human body. We also cite Harvey’s work on the circulation of the blood. What these all have in common is the belief that living organisms are like machines and the laws of physics apply to interpreting their structure and function. 

One of the forgotten contributors to this view of life was Giovanni Alfonso Borelli (1608–1679). Born in Naples, he was the son of a Spanish father, Miguel Alonso, and an Italian mother, Laura Porrello. His father had been exiled from Spain for association with a heretic. This led young Giovanni at the age of 20 to change his baptismal name from Giovanni Francesco Antonio Alonso to the fully Italian sounding Giovanni Alfonso Borelli, which was a version of his mother’s surname Porrello. 

At that time Naples was a Spanish colony and Borelli grew up with his sympathies for Italian culture and political rule. He became a mathematician and astronomer first. He worked out the orbits of Galileo’s discovery of the four large moons of Jupiter and showed they were ellipses. He showed that a comet of 1664 had a parabolic path and was farther than the moon, contradicting church belief then that the comets were not as far as the moon. Isaac Newton cited his work.  

Borelli shifted to medicine and showed that the motions of animals was caused by muscle contractions and the mathematics of levers, pulleys and other machines applied to the components of the body that he studied. He rejected the prevailing view that motion was caused by a vital fluid in the muscles coming from nerves by cutting muscles and showing no such fluids were released. Instead he worked out the center of gravity for different activities of animals and founded the field of biomechanics.  

He kept moving whenever his Spanish ancestry was revealed or when he contradicted fellow scientists who clung to Aristotelian theories that Borelli rejected as nonscientific. In his later life while writing his works, he was supported by Queen Christina of Sweden who went into exile in Rome after converting to Catholicism. He taught mathematics in the convent school that she established and she paid for the publication of his book on animal motion that he dedicated to her.  

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

placozoa

By Elof Axel Carlson

Elof Axel Carlson

Biologists classify living things using a system that Carl Linnaeus (1707–1778) introduced in the 18th century and that has grown in detail over the decades as new forms of life are found and studied. Humans are familiar with being vertebrates (a class of the phylum Chordata). Chordates are animals with a spinal cord, spine or an embryonic structure called a notochord. There are 55,000 chordate species. So far there are 109 phyla covering plants, animals, protozoa, fungi, bacteria and archaea, which are less precisely organized into kingdoms and domains.  

One phylum, first discovered in 1883, consisted of just one species until recently. These are the Placozoa (placo = flat and zoa = animal). They are small (about an eighth of an inch or 1 mm) and are roughly disc shaped with three layers. The top layer has cells with a hairlike thread called a cilium. The bottom layer is also ciliated but has additional cells that take in food from the ocean muck on which the placozoa live. The middle layer has amebalike cells and fiber-bearing cells that contract, making the placozoa lumpy in appearance.  

They reproduce by forming a bud that enlarges and eventually pinches off to produce identical twins. In laboratories, some of the placozoa produce sex cells (sperm and eggs), but these rarely survive the embryonic stage with about 150 cells at the time they die. No such embryos are found in samples of ocean sediments where placozoa dwell. Their DNA has been analyzed and it shows they have a past history of doubling their gene number and rearranging the sequences of their genes as they have moved about the oceans for more than 500 million years.  

Today three species are recognized from samplings around the world. They have about 12,000 genes and portions of these they share with sponges (the phylum Porifera) and comb jellies (the phylum Ctenophora).

Note that the placozoa do not have organized tissues (we have epithelial, muscular, connective and nervous tissues), a basic symmetry (we have a bilateral or left and right sides that are roughly mirror images) or body organs (we have kidneys, lungs, internal bones and eyes, ears, a nose and mouth). They have no nerve cells, muscle cells, bony structure, intestines or sense organs.  

What makes the placozoa interesting to biologists in this molecular era is the opportunity to compare the genomes of related phyla and see what genes they have to work out a molecular tree similar to the trees of life that have been worked out by comparative anatomists since Darwin’s theory of evolution provided a model of how to organize life. They represent the launching state of life before the familiar phyla of sponges, worms and more complex phyla appear in the fossil records.  

Most of the familiar phyla appear in the Cambrian era about 500 million years ago, and the placozoa are first seen in rocks designated as Ediacaran, which existed 100 million years earlier. Rocks can be dated by isotopes present in atoms that have decayed over the millennia. 

Of future interest will be identifying genes in later phyla and genes in placozoa and how they function in these different organizations of life. Also, it will be interesting to follow the genes in placozoa and in their ancestors back to protozoa in the animal kingdom. As interesting as placozoa are, they are too small to be adopted as pets in saltwater aquariums and hard to differentiate without a lens from the muck that accumulates in a fish tank.     

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

By Elof Axel Carlson

Elof Axel Carlson

In 1974 I was a Hill Foundation visiting professor at the University of Minnesota, invited by the History of Science Department to interact with its faculty and students. One faculty member who showed up to my seminar class was Robert Desnick who was interested in medical genetics and he had completed both an M.D. and Ph.D.  

Four years later I arranged with Desnick, who was on the faculty of the medical school, to go on rounds with his pediatric fellows so I could learn what human genetics disorders were like (30 percent of the pediatric patients had some medical genetic condition). I also used my time there to study the genetics of retinoblastoma, a cancer of the eye in children that can affect one or both eyes, and I published two papers with Desnick on that study. I also met Robert Gorlin who had a dental degree and became a world expert on syndromes of the head and neck and whose book on those conditions was a classic (now in its fifth edition).     

I thought about those experiences recently as I read articles in the Public Library of Science (PLoS) on the web about the genetics of the face. All vertebrates have heads with eyes, nose, mouth and ears. I knew from my embryology class as a graduate student that the vertebrate embryo forms a neural tube and one end balloons into a brain. A group of cells along the seamline of the tube migrates and portions of it form the face as do slabs of embryonic tissue that come together to form the skull or cranium. Genes controlling these movements and managing the tissues involved were known from a variety of genetic disorders that Gorlin and Desnick had been following.  

In reading the PLoS articles I felt like Rip van Winkle becoming acquainted with a new world that I had slept through. There are now almost a thousand syndromes of human disorders of the head, neck and face. Hundreds of genes involved have been isolated and sequenced. A smaller portion have had their functions worked out. There is one major gene for cleft lip and palate and dozens of other genes that can modify its severity. Some are tied to a vitamin (folic acid) deficiency and may also lead to spina bifida.  

The story unfolding at a molecular level is still in its infancy but enough is known to make some reasonable predictions. In a few decades it may be possible to examine the DNA of persons (even mummies or the bones of ancient humans) and reconstruct on a computer screen the portraits of their faces as adults. I toyed with this possibility in 1968 in a public lecture I gave at UCLA (50 years go by like a flash when you turn 87). Back then it was all based on speculation.

In 50 years, as the PLoS articles demonstrate, the changes in knowledge are accelerating thanks to the zebrafish (Danio rerio) as a model organism for vertebrate embryology. The zebrafish embryo has transparent cells, so one can look at embryos forming and identify each of the cells involved. 

Biologists have known since Darwin’s writing in the 1860s that facial expressions exist among animals, but humans are remarkable in the nuances facial expressions convey — a Mona Lisa smile, a raised eyebrow of skepticism, a pout, a crying child and the contracted muscles of a bigot shouting slurs are only a few of the many ways we read other people’s faces. At present we can only guess how many genes are involved in these facial gestures. A genetic component is involved because identical twins raised apart for many years show remarkable similarity in their facial expressions and mannerisms.    

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

We are now in a molecular age in which individual genes can be sequenced and their functions studied.

By Elof Axel Carlson

Elof Axel Carlson

You are a multicellular organism. In fact you have about 37 trillion cells. That’s 37,000,000,000,000 if you like numbers. Cells were first described in 1665 by Robert Hooke who looked at cork bark under a crude microscope he had invented. The cells he saw were empty boxes. He believed this was the cause of cork’s buoyancy. 

It wasn’t until the mid-1800s that lenses and stain technology developed to reveal detail inside cells. It also permitted several biologists to promote a theory that all cells arise from pre-existing cells and that organisms are composed of cells. 

In that stage of our knowledge of life, scientists worked out mitosis (how cells divide) and meiosis (how cells form reproductive cells). They learned that chromosomes carried the genes, or hereditary units, that produce all the components and cellular types in an organism. In the last half of the 20th century they learned how to take apart and put together components of the living cell. 

We see multicellular life among plants and animals around us, but we cannot see single-celled organisms without a microscope. Microscopic single cells exist for bacteria, certain algae, certain fungi and most protozoa. The presence of multicellular organisms goes back to about 2.5 billion years ago with filaments of cells in ancient rocks.  

About 20 years ago I was delighted to read about experiments by Nicole King (UC Berkeley) showing that one-celled organisms, similar to those found in sponges, could be selected to join in clumps. That has been greatly extended to algal cells (Chlamydomonas, Volvox) and fungi (yeast). 

William Ratcliff at Georgia Tech recently published results of selection for larger and heavier yeast cells that settled down on the bottom of test tubes. He isolated some that developed adhesions. From continued selection (hundreds of generations of yeast) he obtained some that formed flakelike arms or branches and that reproduced by breaking off branches. 

King, who continues her work, has isolated more than 300 genes associated with multicellularity, many of them found in single-celled organisms. By combining different groups of genes, she can increase the likelihood of producing multicellular units.  

Multicellular organisms can be simple like balls or they can be complex with specialized tissues and organs. They can dig deeper into the earth or extend their range from a few feet to miles or across continents. There have been millions of species that constantly change the way the surface of the earth appears. We are now in a molecular age in which individual genes can be sequenced and their functions studied. 

If I see a picture of myself, I see my surface of skin and hair clothed or unclothed. With X-rays I can see my bones, but not as well as a human skeleton mounted in an anatomy laboratory. I have seen what my tissues look like from a box with a hundred or more slides that I studied at NYU as an undergraduate. 

I have lived through the discoveries of identifying my genes as made of DNA, and we are now capable of sequencing them and understanding what they do. Each finding adds to both our medical knowledge for pathologists and to basic science in understanding how a living organism works.  

I would not be surprised to see experiments that will produce synthetic multicellular organisms using genes from different organisms to produce differentiated cells for each task desired. It will be a biological engineering that goes beyond applications to the pharmaceutical industry. Think of them as microscopic or miniature tools. Imagine tools snipping away tumors less than a millimeter in diameter. Imagine such tools extracting and expelling miniature pellets of gold and rare metals from ocean water. 

For those who worry about unintended consequences of applied science, two things are important to consider. Such experiments should be well regulated by ethical and safety review boards by universities, hospitals and corporations. The odds of such synthetic organisms are remote. Similar safety concerns in the 1980s accompanied the development of genetically modified bacteria and yeast cells, which today continue to produce human insulin for diabetics, human growth hormone for children with pituitary hormone deficiencies and hundreds of other modifications.  

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.

Silkworms are popular among Japanese geneticists because of the silk industry.

By Elof Axel Carlson

Elof Axel Carlson

I got my doctorate working with a model organism, the fruit fly, Drosophila melanogaster. It was introduced to science about 1905 at Harvard where William Castle and his students studied the wing veins of these flies for subtle changes that Darwin’s theory of natural selection proposed. Castle suggested to Thomas Morgan at Columbia that he could use fruit flies for a study of mutations that Morgan hoped to launch. 

Morgan was luckier than Castle because his use of fruit flies led to the discovery of sex-linked inheritance and a process of shifting genes between matched chromosomes. It led to the chromosome theory of heredity and the theory of the gene as a unit of inheritance present in chromosomes.  

Botanists found corn or maize (Zea mays) an ideal organism and classical genetics had inputs from both fruit flies and maize. The most famous contributor to maize genetics was Barbara McClintock who worked out a field of cytogenetics by isolating structural components and consequences for broken chromosomes that experienced rearrangements.  

The bacteriophage viruses and bacteria like Escherichia coli were major contributors to molecular biology. Bacteria are cells but viruses are not. Viruses do have a life cycle, living as destructive parasites or beneficial insertions into bacterial chromosomes. Bacteriophage studies confirmed many of the predictions of DNA as the chemical basis of heredity. They also confirmed that a virus’ proteins are not needed to produce the proteins of its progeny. 

The flow of information goes from the genes as DNA to molecules of RNA carrying the genetic messages to cellular units that translate them into proteins. Bacteria were also used to work out how genes are switched on and off, an important process that regulates how cells work. Most of these early studies in molecular genetics were initiated by Max Delbrück for bacteriophage viruses and by Joshua Lederberg for bacteria. 

For higher organisms a life cycle involves fertilization of an egg by a sperm and the formation of an embryo, which forms different organs with the resulting baby turning into an infant or child and eventually a mature adult and lastly an aged or senescent individual who dies. Sydney Brenner in 1963 suggested using a nematode, the roundworm found in the soil, Caenorhabditis elegans, to work out how this life cycle can be studied at a molecular level. They are similar to the roundworms called vinegar eels seen in flasks of organic apple cider vinegar.  

A fruit fly

Genetics is a composite of the work with many different organisms in plant, animal, and microbial worlds of life. The designation model organism for research biologists distinguishes the usage of research organisms. Applied genetics is often used with specific purposes in mind that benefit the economy. Silkworms are popular among Japanese geneticists because of the silk industry. Tomato geneticists are interested in color, flavor, texture, size and shelf life as they are for most vegetable crops, applying genetics to improve varieties.  

Model organisms were chosen to explore the biology, especially the genetics, reproduction, embryology, metabolism, neurobiology or other fundamental ways living organisms have adapted to their environments and evolved. Biologists working with model organisms often find that once the basic biology is worked out it can be applied to benefit health and the economy. It may take decades before that happens.  

When Calvin Bridges in Morgan’s laboratory found extra or missing chromosomes associated with fruit flies, he did not know that some 40 years later extra chromosomes would be associated with birth defects or disorders in humans such as Down syndrome (trisomy 21) or Klinefelter syndrome (XXY males).  

In some ways humans serve as a model organism. Linus Pauling was interested in how red blood cells carry oxygen from the air and discharge carbon dioxide into it. His curiosity led to a working out of the structure of the hemoglobin molecule and its mutational difference when healthy individuals have their hemoglobin analyzed and compared to that of persons with sickle cell anemia. Pauling called sickle cell anemia a molecular disease. Note that Pauling’s motivation was not that of a physician seeking a cure for a disease but that of a chemist seeking the molecular basis of how we breathe and why oxygen and carbon dioxide ended up exchanging places in red blood cells. 

Humans are also model organisms for the field of neurobiology, especially for processes like memory, learning, association, pattern recognition and speech, most  of which would be difficult to infer from the study of a roundworm’s much limited nervous system. This human study is more likely to be at the physiological and anatomical level rather than the molecular level because there are numerous brain injuries and genetic disorders of the nervous system that can be used to identify where to look for these functions.   

Elof Axel Carlson is a distinguished teaching professor emeritus in the Department of Biochemistry and Cell Biology at Stony Brook University.