The One with Mendel and his Peas

Around the same time as Miescher was tinkering with DNA in Tubingen castle, a middle aged friar-scientist Gregor Mendel was experimenting with inheritance of pea plants. He was the first to define a set of mathematical rules behind inheritance that birthed the field of genetics - a field that lay dormant for a few decades before exploding in the 1900s, and continues to develop to this day. Genetics gives us the tools to reshape the living world with intention and at speed. 

Episode Transcript

(00:00):
History is full of funny twists and turns with unexpected connections.

(00:04):
And so it is that perhaps if it wasn't for Josiah Weddwood's genius for ceramics and capitalism,
that the history of GMO's might have run a little bit differently.
Josiah Weddwood, of Weddwood pottery fame, had a son, John, who used his inherited wealth
to found the Royal Haltacultural Society in London in 1800.

(00:25):
The society did and still does all the things you might imagine from a Haltacultural Society,
promoting gardening, helping to open botanic gardens, hosting competitions,
and they also hosted groups of experts in conferences to share their work,
and publish the conference proceedings to share with the broader community of both scientists and
gardeners. And so it was that in 1906, one William Bateson walked through the impressive columns of

(00:52):
the entrance to 80 Fintcent Square in central London, the headquarters of the Royal Haltacultural
Society. This wasn't his first time in London, though he did grow up far away in Northern England.
But by this point in his life, he was running a semi-formal research laboratory at Cambridge University,
Norfar from London, and he was well connected into a very passionate but still not too large group

(01:15):
of scientists, who all agreed that they were onto something pretty important. Bateson was among the
very first few British scientists paying attention to work published at the very end of the 19th century
by Dutch scientists Hugo DeVries and German scientist Karl Korrens. DeVries and Korrens
had both independently done work that was quite similar to the decades-old research by Czech

(01:38):
scientist Gregor Mendel that had been largely ignored and forgotten over the intervening decades.
For whatever reason, the idea of genetics have been bouncing around in the minds and the
experiments of different European scientists and all came together in the 1900s with DeVries and
Korrens publishing their work and in the process highlighting and adding to the prior work of Gregor Mendel.

(02:00):
Bateson was 40 when this rediscovery of Mendel happened. He'd studied biology and gone off to study
zoology in the United States for a few years, then come back to study development of vertebra
animals at Cambridge University. We'll hear a little more later in the episode about how Bateson
switched his research to genetics but suffice to say he threw himself into it and was rapidly making

(02:23):
a name for himself. So it wasn't a great surprise that he was invited to give an address at the 1906
third international conference on plant hybridization at the Royal Halticultural Society.
But I think that even he would probably be surprised that today the conference has been renamed
after the fact. Instead of the original title conference on plant hybridization, it was renamed

(02:45):
using the word he proposed for the gathered scholars in his opening address. And so it is now recorded
as the third international conference on genetics. Welcome to Modified. I'm your host,
Dr. Rolander D'Alaange. I've worked for 10 years in plant biology and energy research,
worked that sometimes involve making genetically modified plants. Now I'm a science teacher,

(03:08):
training students for future careers in biotechnology and other areas of life science.
This podcast is my attempt to share some of what I know and how I think, to guide you through the
science of GMOs and hopefully just enough of the history and the social context to give you
a path forward in your own thinking. And if all else fails, I hope you'll enjoy some of the
surprising stories and fascinating facts in the world of genetically modified plants. This is

(03:32):
episode three, the one with Mendel and his piece. If you're tuning in for the first time,
I recommend heading back to episode one and starting there. Otherwise, let's go on.
If you've ever studied genetics at school, there's a good chance it was introduced to you via
Gregor Mendel and that you learned about things called alleles, represented by big letters and small

(03:53):
letters like big A, little A, big B, little B. And maybe you drew little matrices called
punnetsquares to track how combinations of big B and little A might combine with big A and little B
among theoretical offspring. And then I have to answer questions about what percentage of offspring
would be yellow or green, tall or short. You would have learnt that genetics is formulae,

(04:18):
tables and percentages. Essentially, the genetics is math. As a side note, it did take me roughly 10
years to be able to say math instead of maths, but I finally did it. Thanks to all the Americans who
never gave up on me through those years. So if you learn that genetics is math, you're not alone
and you're not wrong. To this day, a lot of people who study genetics do so using mathematical tools

(04:39):
and concepts, though the sort of mathematical tools that require a lot of computer code and
processing power rather than punnetsquares. And the reason this mathematical concept of gene
genetics is often taught first is because that tracks the history. Gregor Mendel never heard of DNA
since as we learned in episode one, it was only just being isolated of the first time when he was

(05:02):
doing his research in the 1860s. He certainly knew that organisms made up cells, but all of his work
was about finding mathematical ways to describe biological phenomena without any clue what the
material basis was for these phenomena. And that is how things continued for many decades.
The molecular viewpoint, what we learned about last episode, genes as units of this physical

(05:24):
thing called DNA, didn't become dominant until the later 20th century. So let's step back in time
a little back to Mendel's world. He didn't work with microscopes in chemistry labware, like Friedrich
Misha. His tools were pencil and paper, patience and careful observation, and words. Yes, words can

(05:45):
be very important tools in all fields of science, really in any kind of specialist area of work.
Special words, what we call jargon, can be created on the spot or maybe coined by slightly
modifying existing words. And perhaps the most annoying situation is where a common everyday word
gets repurposed by specialists in a particular field to mean something quite specific and

(06:08):
quite different from its everyday use. That is certainly unhelpful for newcomers trying to
get to grips with the literature, and there are lots of these false friends in genetics.
One you might be familiar with is dominant. The meaning in genetics isn't a million miles from
the common usage. Dominance was one of Mendel's key discoveries. He made this discovery

(06:31):
in painstaking observation of the inheritance of traits of pea plants in the monastery gardens
of St. Thomas's in Bruno. In what is now the Czech Republic in the late 1850s and early 1860s.
He found that in many cases where you had different versions of a trait, for example,
white or purple flowers, one version seemed to dominate the other in crosses, meaning all the

(06:54):
offspring had purple flowers even when you crossed a parent plant with white flowers to a purple
flower parent. Try saying that ten times fast. The more he observed carefully encountered the ratios
of purple to white, the more he found that his dominance relationship was something quite specific
that would yield reliable ratios. White and purple parents would yield all purple offspring,

(07:18):
crossing two of those purple flowered offspring together would give you an exact ratio of three
purple flowered plants to one white flowered plant. For millennia, people had known that
traits are inherited, and it certainly seemed that this process was not some exact blending of
parents, but to most people who had spent much time thinking and writing about inheritance,

(07:41):
they couldn't come up with any really defined rules. And that included Charles Darwin,
who thought about it a lot and even spent a lot of time studying it as part of his work on evolution.
But even Darwin seemed to give up on having anything more precise to say than that somehow
traits are combined from both parents. Mendel found mathematical rules that could be used to trace

(08:02):
unknown biological processes, and he coined words like dominant to conceptualize and track
what was going on. Stepping back into school mode and that hypothetical introductory genetics class
you might have taken, what other words might you have heard? Generation, back cross, recessive,
heterocygote, and what about that one we started with earlier? Alleele. Alleele's are a key innovation

(08:28):
of Mendel, without which the concept of dominance doesn't make much sense. Many people are aware that
in humans we have two copies of our genomes in most of ourselves, two basically identical copies,
except that there can be slight variations between the two. Mendel didn't use the word gene
or actually the word allele, he used the word factors, but he conceptualized that like people,

(08:53):
his pea plants had a bunch of different genes, and for each gene they had two copies.
These copies could be slightly different from each other, and these different varying
inversions of any given gene are what we call alleeles. He just referred to them as dominant and recessive
factors associated with a particular trait. A given plant might have two identical alleeles

(09:19):
for a given gene, or two different ones. So if there's a flower color allele, a given plant might
have two identical purple flower alleeles, two white flower alleeles, and one white, one purple.
But in that mixed case, what we call a heterozygote, you'll see only purple flowers on that plant,

(09:40):
because purple is dominant over white. These are not things you can look at and touch,
there are ways of thinking about and tracking inheritance, and also of predicting inheritance.
They can only exist relative to other things. Alleeles for example are different variations of
the same gene. They have no meaning outside of the existence of other alleeles. This makes them I

(10:03):
think a little more elusive to grasp. This way of thinking about inheritance is less intuitive,
and I think less appealing than the physical materiality of DNA that we looked at in episode two.
Dominant seems somewhat strange and magical. Why would genes work this way?
Well, once genetics could be combined with molecular biology to create molecular genetics in the

(10:27):
later 20th century, this became more clear. In fact, in any given population, you might find many,
many alleeles of a given gene, meaning many versions of that gene with slight DNA differences.
Most of these differences will have no impact on function, and so if like Mendel,
or you can see the visible features of the plant, most of those alleeles will be invisible.

(10:51):
Only the differences with a dramatic impact will likely have a visible effect on traits.
And in most cases, a dramatic random variation in a gene will simply break its function,
by scrambling something about the DNA code that will lead to a different and usually worse version
of the protein it codes for, or perhaps stop any protein being produced at all.

(11:13):
Random DNA variations are called mutations. A major mutation might, for example,
be in the regulatory sections at the beginning of a gene, and might stop the gene even
functioning as a gene anymore because the cell's molecular machinery no longer has a clear
start point for making RNA copies of the gene. So if you have two alleeles, one the normal

(11:35):
functional version of the gene, and the other is so broken it doesn't produce a protein at all,
only one of them will end up influencing the visible traits of the organism.
That is the functional one. The mutated one will be basically hidden.
It will be recessive to the dominant functional version, and that's why this dominant
recessive relationship is fairly common. Simple dominance is just one of many options. There's

(12:01):
co-dominance, incomplete dominance, epistasis, the list goes on. And can you imagine how complicated
it would be when you're dealing with one of the many organisms that have more than two genome
copies per cell? Breadweat, for example, has six copies. That means up to six different alleeles
of each gene in a given wheat plant. These complexities kept geneticists very busy and very

(12:23):
confused in the early decades of the 20th century. Luckily, Mendel was working with pea plants that
like us have just two genome copies per cell, and he found some traits to work on that have a
leal pairs with simple dominant recessive trait combinations, and where that one gene can exert
a strong effect on a visible trait like flower color, making it easy to track over time.

(12:48):
Focusing on these simple cases allowed him to draw some important and powerful conclusions
about genetics, but it was very far from the complete picture, really what he did was just the beginning.
Deneetosis in the early 20th century had to try and dive into all of the messy complexity of inheritance
patterns, without any idea of the materiality that might have made some of it a lot easier to understand.

(13:11):
However, they stuck with the challenge, and in the process they created mathematical approaches
that could be used to predict even quite complex inheritance patterns, and that can be far more
useful than being able to just describe the molecular processes of the DNA RNA protein relationship.
We can imagine pieces of DNA inside cells, and how that DNA is made up of different letters,

(13:33):
A, G, C, and T, and how those make up things like words and sentences, the DNA is inside cells and
get passed from parent to child. But that neat mental image isn't actually a very useful if what we
want to do is predict exactly what will happen, if you take two individuals, for example,
two different varieties of maze and cross them, if one maze variety is tall with red

(13:55):
kernels and is resistant to mildew, the other variety is short, stout, flowers later in the end
has yellow kernels, what exactly will the progeny look like? Hopefully you can see from this example
why questions about inheritance, and not just academic preoccupations, but are driven by very
material, very physical concerns, making food, and yes, making money. I don't think it's a

(14:20):
tool surprising, the person who first defined predictable rules of inheritance, and methods that
can be used to define inheritance patterns of any given trait, did it by studying a crop plant,
the garden pea. That person, I should be very clear by now, was Gregor Mendel, a scientist who
was also a clergyman, working in Austria in the mid 19th century. He was more specifically

(14:42):
an Augustinian friar, from the same Catholic order as the current Pope, Leo XIV. Mendel became a
friar because it was a good way to have his school tuition covered, so that he could pursue his passion
for science. From what I know about Pope Leo, which is very little, he was pretty committed to the
bit of religious service from a young age, Mendel seemed to be a devout Catholic, but also just as much

(15:05):
a devoted teacher and scientist. Unlike Friedrich Misha, Gregor Mendel did not come from a family
of doctors and scientists, but farmers. Farm owners were the decent amount of money, and have to
invest in their children's education. Financial privilege has long been a huge help to scientific
careers, though thankfully these days it's not a requirement. Also, unlike Misha, he didn't spend a

(15:30):
long career focused on one fairly narrow field. Instead he had a fairly short career that bounced
around from physics to botany. He taught science at a local school in Bruno, and he kept himself
well informed on a number of topics, including reading Charles Darwin's work on evolution.
And perhaps because of his family's farm, as well as his own work in the monastery gardens,

(15:52):
he was well aware of the realities of running a farm and was up to date on agricultural research.
And drawing on all of his knowledge and experiences, and supported by friends and colleagues,
he started a set of experiments in the 1850s that are generally pointed to as the birth of genetics.
And all he did was grow garden piece. Grow them, carefully observe them, cross them in different ways,

(16:16):
and record all of the data. And then crucially, try to make sense of what he was seeing in light of what
he knew about biology. Actually a pretty classic scientific workflow. Look up a history of genetics,
and you'll probably read the Gregor Mendel, more or less invented genetics from Finneir as he worked
on his pea plants in the 1850s and '60s. As I just said, his work is generally cited as the birth of

(16:41):
genetics. However, historian of science come away, and yes, I do not know how to pronounce that last name,
I apologize, to any of the sircles out there, writing in 1951, in an article on Gregor Mendel,
his precursors, described the scientific context that Mendel worked in and was influenced by.
Mendel was building on multiple ideas from earlier scientists, including many of

(17:04):
the scientists who like him worked at the intersection of science and agriculture. That includes
the work of Augustine Sagare, who showed that when crossing melon varieties, some traits were
dominant. Sagare wrote that traits don't get blended together, they seem to be controlled as
discrete entities. Sound familiar? Mendel also knew about the work of Johann Cizaron, who studied honey

(17:29):
bees. Cizaron looked at crosses of bees. Male bees hatched from unfertilized eggs, and he recorded
then all cases, male bees fully resemble the mother. However, female bees hatched from
fertilized bees, and he shows, however, female bees hatched from fertilized eggs, and he showed

(17:49):
the resulting female bees don't have traits that are a blend of both parents, but looking at specific
traits, he found that 50% of the daughter bees looked like the male parent, 50% looked like the female
parent, a one-to-one predictable ratio. Studying ratios of inherited traits was the central method

(18:10):
that Mendel used to define his laws of inheritance, and it didn't just come from nowhere.
There he was building on the work of others does not diminish Mendel's contributions. It is just how
research works. It isn't done in a vacuum. Similarly, Charles Darwin wrote out his theory of the mechanism
behind evolution after decades of scientific interest and research into the basic principle of evolution

(18:34):
and building on work that described theories that were quite similar to Darwin's.
One of Darwin's great contributions, like Mendel, was that he spent a long time gathering data
and describing his findings clearly. Mendel, for the first time, articulated a number of rules
of inheritance backed up by data from multiple experiments. Sadly, his research remained pretty

(18:57):
underappreciated for about 30 years, and so the critical mass of scientists in the early 20th century
finally understood what Mendel had done, and then pretty furiously built on his work to spawn the field
of genetics. I have been hinting at ideas so far that genetics can be approached from two ways,
as a set of mathematical tools to track inheritance, and as a study of the physical hereditary

(19:22):
material, aka DNA, and all the other physical things that it can interact with. And actually,
these two tracks developed in parallel, and until they could be, and actually those two tracks
developed in parallel, until they could be properly synthesized from the 1950s onwards.
Friedrich Misha isolated DNA in the 1860s. The structure of DNA was solved in the early 1950s.

(19:49):
Mendel defined the laws of inheritance in the 1860s, but genetics only really got going as a field in
the 20th century, developing directly alongside molecular biology. The two ideas of a gene,
the physical stuff, the DNA that's ready to make proteins, and the mathematical stuff,
the predictable statistical relationships that connect the traits of offspring and parents.

(20:12):
They were developed and continued to be developed together. Both conceptual frameworks
are still important and useful within biology. To the rest of this podcast, we'll be leaving behind
the 19th century, planting ourselves firmly in the 20th, before bringing things up to the present
and the near future in the end of season one. I promise that I do want us to get to plant

(20:35):
transgenics and the GM crops that exist around us today, we won't be just meandering through
history. But we will make one brief stop back in 1906. We'll check back in with our still relatively
up and coming, but already influential, William Bateson. He is taken to the stage in London and
the conference devoted to the study of plant hybridization. He speaks for almost an hour in total,

(20:59):
but it is in fact only a few minutes in that he offers up a suggestion of a word that might serve
as a term for their field of research. Genetics. His speech isn't about his own research,
instead he's been invited to help provide a summary of the whole field, the key ideas and
breakthroughs, and to hopefully inspire the gathered researchers to keep on pushing through

(21:21):
the inevitable failures and inevitable confusion. Towards the end of his speech, he addresses
the biggest sticking point, spinning a negative into an inspiring call for action.
After discussing some of the key principles of inheritance that are driven by some mysterious
units or factors, he advises the gathered scientists. Ever in our thoughts, the question rings,

(21:47):
what are these units that bring all this to pass? Color, shape, habit, power of resistance to
disease, and many another property that might be named? How the pack is shuffled and dealt,
we begin to perceive. But what are they, the cards? Wild and inscrutable the question sounds,
but genetic research may answer it yet. This speech is generally regarded as the point

(22:12):
that the field of genetics got its current name. Before that, a whole range of names were used,
focusing on processes like hybridization or inheritance. It may seem strange because if you
look up the conference, it is recorded as the third international conference on genetics. Why would
you call it that if the name didn't even exist yet? But the name was applied retroactively because

(22:35):
of Bateson's speech. Naming the field of genetics was very far from Bateson's only contribution. He
led a pioneering research team at Cambridge University in the UK in the first decade of the 20th century.
In fact, both his mother and father were influential at the university. His father was an academic
and a college master, basically the head of a college. His mother was a suffragist and one of

(22:59):
the founders of NUNUM College, which is to this day a woman's only college. So just like Misha,
it's hard to ignore the influence of upbringing on Bateson's life opportunities and his interests.
And we can see a particularly strong connection for Bateson, and that he specifically ran a research
group at NUNUM College, the college his mother helped to create. It was actually an all female

(23:22):
research team apart from Bateson, included his wife and his sister-in-law, Florence Durham,
who was one of the leading scientists in the group. If you hadn't already guessed, they worked on
hybridising plants and animals to study Mendelian inheritance patterns. He was not the sort of researcher
to content himself with publishing work and just letting the work speak for itself. He was a

(23:45):
passionate advocate for his own specific way of understanding inheritance, where he saw,
as the only correct way, the way that Mendel had shown the world decades earlier.
The core of the Mendelian view was that all traits are based on discrete units of inheritance.
What would come to be called genes during Bateson's lifetime, and that these genes can change over time,

(24:09):
but not gradually and subtly, instead new genes or new gene invariants appear suddenly,
causing new traits to appear in a lineage. This view contrasted with many others in the field,
who believed that change was gradual and subtle and hard to pin down to a specific gene.
We now know that in fact both ideas are correct, it just depends on the particular gene and the

(24:35):
particular trait, and the types of DNA mutation involved. You might find evidence of gradual change
over time that cannot be pinned down to a single gene, in fact that is the more common scenario.
But there are still plenty of cases that follow that kind of Mendelian model, where dramatic changes in
traits can arise quite suddenly and be traced to a single gene. And as we'll see in future episodes,

(25:00):
in a modern biotechnology laboratory, it's possible to modify or insert a single gene to create
very profound effects indeed. Still, most traits are controlled by many genes, interacting with each other
and the environment, so that you tend to see if you look at variation at the population level
over time is a lot of diversity with traits shifting gradually over time.

(25:22):
Anyway, back to that conference. I wanted to share another slightly longer excerpt of what he said
to his fellow scientists gathered in the conference hall in London in 1906.
It's a section just before when he calls for genetics to be the new official name for the field,
so early on in his speech. Here's what he said.

(25:44):
When formerly, we looked at a series of plans produced by hybridization, we perceived little but bewildering
complexity. We knew well enough that behind that complexity, order and system were concealed.
Glimpses indeed are pervading order, were from time to time obtained, but they were transient and
uncertain. As casual prospectors, we picked up occasionally stray nuggets in the sand, but we had

(26:11):
not located the reef, nor had we any machinery for working it if discovered.
Then came the revelation of Mendel's clue, with all the manifold advances and knowledge to which it
has led. The most protean assemblage of hybrid derivatives no longer menaces us as a hopeless enigma.
We are sure that even the multitudinous shapes of the cucurbits, or the polychromatic

(26:36):
hues of orchids, would yield to our analysis. Thus the study of hybridization and plant breeding
from being a speculative pastime, to be pursued without apparatus or technical equipment in the hope
that something would turn up, has become a developed science. Destined as we believe, not merely to

(26:57):
add new regions to man's knowledge and power, but also to absorb and modify profoundly
large tracts of the older sciences. Look at the language he uses, he talks about machinery,
apparatus, equipment, and how these bring power. But he isn't describing physical machinery here,

(27:19):
he isn't even talking about the physical material of inheritance, the DNA that forms genes,
or the proteins that are made from DNA blueprints. He was speaking decades before the physical
model of the gene could be connected to Mendelian inheritance. No, instead he was talking about the
concepts of the mathematical techniques developed first by Mendel and then by many after him,

(27:41):
including Bateson and his team at Cambridge. And while Bateson is definitely a bit dramatic in
general, I don't think he's wrong about this. Genetics was and still is a powerful machine
to both understand the world around us and to shape it. The impacts of genetic research are far
reaching and include many application areas, not least among them human health and disease.

(28:06):
They're given the focus of this podcast, I want to highlight the strength of the connection
between crop plants and genetics right from the beginning. And you can see it in Mendel's work
on peas and in Bateson's. And in particularly emblematic of this connection is the fact that in 1910,
four years after the conference that coined the word genetics, Bateson left his work at Cambridge

(28:29):
to become the first director of the newly created John Innis Horticultural Institution,
now the John Innis Center. It was originally founded seemingly without a lot of thought put into it,
from money left in the will of a London property developer, to be some sort of horticultural
and agricultural education and research institute. Bateson instilled genetics into the core of the work

(28:52):
of the John Innis Center, something that is just as true today more than a century later or that work
carries on. Right from the start, the genetics work that Bateson promoted at the John Innis Center
was connected directly to real world applications, to understanding how plants work and developing new
ways to harness the conceptual framework and mathematical tools of genetics to breed new and

(29:16):
improved crop varieties. Bateson saw a new world of agriculture, one in which any crop could be
created if you made sure to follow the right steps, deploying the powerful machinery of genetics
to shape the raw material of nature. As we'll see, the GM crops we know today rely on specific

(29:38):
laboratory technologies that did not exist in Bateson's time, and that we, and that he would have
struggled to comprehend. But I think he would have seen the clear line back to his advocacy and his
research at the intersection of agriculture and genetics. Thank you for listening to Modified.
This was Episode 3, the one with Mendel and his piece. It was written by me, Orlando D'Angelge.

(30:03):
I used many sources to help me research this episode. I want to particularly acknowledge
three of them. Do you missifying the mythical Mendel, a biographical review by Daniel Fairbanks 2022?
Mendel and his precursors by Conway Circling, 1951. And I want to thank the biodiversity heritage

(30:23):
library based in the Smithsonian in Washington, DC, on whose online archive is available
the proceedings of the third international conference on genetics, including William Bateson's speech.
This is a tiny one-person podcast, so please, if you're enjoying it, leave a review and tele-front.
If you have notes, I'd love to hear them. And you can email me at [e-mail]. That's

(30:47):
O-R-L-A-N-D-O at ModifiedPod.com. I'm planning to add in an extra episode after Episode 5, just
devoted to answering listener questions. Episodes 4 and 5 will kind of zoom in on plant genetics
in the context of plant biology. And then from episode 6, we'll shift gears to talking more specifically

(31:11):
about crop plants and agricultural science. So send me in your questions about genetics and about
plant science, and I'll pick a few to dive into detail on in that special episode.
So that's your questions on genetics or plant science. Doesn't have to be about something I
mentioned in the podcast, so definitely can be. And you can email those to [e-mail].

(31:35):
As always, you can find out more about me and about the podcast at the website that's ModifiedPod.com,
Modified.pod.com. That's the end of the day's episode. I'll round things out with my five
take-home messages, so if you're stopping here, thanks for listening until next time.
For those sticking around, here are your five take-home messages. One, classical genetics is the

(32:02):
study of inheritance, trying to define rules of inheritance using mathematical tools to analyze
and predict inheritance patterns. An allele is a version of a gene. Dominant alleles are visible in
the traits of an organism, even if they are in heterozygos. Four, genetics research was initiated by
Mendel in the 1860s, but dormant for decades, picking up rapidly from 1900 and continuing as a

(32:28):
major field of biology to the present day. Number five, breakthroughs are rarely isolated and the
product of one person's work is said scientist work in teams and build off of prior related work.
That's all for now. Bye!
Bye!
(upbeat music)