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Summary History of Biology - Lecture 5
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History of Biology – Lecture 5: From generation to genetics07-03-18
End of 19th c. The problem of generation:
Generation was a broad problem in biology that consisted of:
- How does an embryo come to be and how does it grow?
- What is passed down during every cell division?
- How do organisms inherit characteristics?
- What is the relation between heritage and evolution? generation was much
more than just genetics.
In contrast, after 1920: ‘genetics’.
19th c. ideas about heredity: Darwin
Darwin’s speculative pangenesis theory; all cells have ‘gemmules’ which are
somehow mixed when passed down to offspring
Obvious objections:
- Why do blood transfusions not change heredity?
- That means that variations are mixed and diluted, so how can variations ever
stabilize?
Germ plasm theory by August Weismann: germ plasm (gamete) is different from
somatic cell.
Only germ plasm is capable of passing down characteristics, independent of what
happens to the somatic cell.
Gregor Mendel (1822-1884):
Augustinian monk, son of a farmer, became the abbot of a monastery in Brno, Czech
Republic.
The monastery was a local center for science and agricultural knowledge.
Mendel studied physics, theology, agriculture, among others.
Became a teacher, meteorologist (to support agriculture).
- Crossed bees and plants which led to Mendel’s laws (kruisschemas)
o Most famous experiment: crossing of peas.
Few problems:
- Debate whether Mendel was the first discoverer.
- Debate whether Mendel understood his own laws.
o Did he understand that there were 2 alleles?
Priority: who discovered it first?
The story of Mendel, again illustrates the importance of priority: be the first to claim
your discovery.
Recognition is an important reward, which often leads to priority conflicts.
Other examples:
- Watson + Crick
, - Darwin + Wallace
- Newton + Hooke
- Pasteur + Koch
Do mutations occur in leaps, or gradual, small steps?:
Ca. 1900, big discussion in heredity saltationism vs. gradualism:
- Saltationism: saltatio means ‘jump’ large amounts of mutations, which
occur very quickly (even in one single generation).
- Gradualism: mutations occur gradually, not very quickly/dramatic
(comparable to uniformitarianism vs. catastrophism – geology, lecture 3).
Thomas Hunt Morgan (1866-1945):
American biologist. Southern aristocrat, from an impoverished family after the
American Civil War.
Studied zoology and initially specialized in marine biology.
In the zoological laboratory of Naples, he came into contact with experimental
embryology.
At Naples, embryologists often worked with marine species.
Studied biological problems on embryology in Naples which was the key question at
the time.
In 1904, Morgan became professor of experimental zoology at the Colombia
University in New York. There he got interested in inheritance, mutations, Mendel
and evolution.
A convenient organism for studying these questions, was Drosophila melanogaster,
which was then already used by other biologists.
Morgan tried creating mutations by radiation, in order to find and test Mendel’s
patterns.
The fruit fly (Drosophila melanogaster) as an industry:
Drosophila became one of the most popular model organisms:
- Simple and easy to grow
- Clear research questions, rapid publication, large research output
- Linked with theoretically relevant questions of genetics to guide the research.
o Morgan’s research (mapping the genes of Drosophila) was seen as
‘normal science’.
Morgan is considered ‘The founding father of Genetics’.
Orthodoxy (juiste leer) occurs, through:
- Production of research
- Organization
- Identity
- Important applications
- Finance
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