Chapter 7: Genetics Enters The Picture

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Chapter 7Genetics Enters The Picture

• Presented By Tyler Kartzinel
• October 4, 2007

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Outline

• Review of science and public opinion
• Skepticism about science
• Misconceptions and human evolution
• Religion in Evolution
• Chapter 7 Summary
• Sir Francis Galton
• Hugo de Vries
• Gregor Mendel
• Thomas Hunt Morgan and Lab
• Questions
• Return to science and public opinion

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Scientific Questions and Public Impressions

• Flat Earth Hypothesis
• Offer alternative explanations for
• The shape of Earth
• Solar system
• Seasons
• Eclipses
• Gravity
• Shadows
• "It's easy to see how a photograph like that
  could fool the untrained eye. Samuel Shenton

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Scientific Questions and Public Impressions

• Flat Earth Hypothesis
• Oliver the Human-zee
• Oliver is a habitually bipedal ape that has
  captured the imagination of both laypeople and
  scientists. He has been touted as a relict
  australopithecine, a bigfoot, or even the result
  of a clandestine human-chimp hybridization
  experiment.

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Scientific Questions and Public Impressions

• Flat Earth Hypothesis
• Oliver the Human-zee
• The God Gene
• Some humans may be genetically predisposed to
  mystical episodes interpreted as religious
  experiences.

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Can Genetics Help Answer These Questions?
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Sir Francis Galton(1822-1911)

• Rejected
• blending inheritance
• heritable acquired characters
• Heredity
• Soft acquired characters
• Hard unchanging
• Usurped Darwins gemmules as germs
• The Quantifier
• Promoted selective human reproduction (Eugenics)

How come people with large inheritances tend to
spark new thought about heritability?
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Hugo humorless de Vries

• Studied hybridized primroses at University of
  Amsterdam
• Hybrids appear jump from one species to another
• Suggested stress can cause jumps and origins
  for species
• Described Pangenes
• Awarded the Darwin Medal (1906) and Linnean Medal
  (1929)

Research led him to Mendel (but not academic
honesty) Modesty is a virtue, yet one gets
further without it
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How Will History Remember You?
If youre honest
If you steal
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Gregor MendelLets back up half a century

• Conducted extensive plant breeding experiments at
  his monastery (30,000 plants!)
• Considered seed shape, interior color, skin
  color, pod shape, pod color, flower position, and
  plant height.
• Results From pure parents there was no blending
  in offspring but a dominant trait was inherited.
  When hybrids are bred with their own type they
  develop 31 trait ratios
• Peas were considered a special case because in
  other plants hybrid traits did blend.
• Multiple characters independently segregated.

• Interestingly, Mendel tried to repeat his results
  with evening primrosebut failed.

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IN THE EARLY DAYS OF THE 20TH CENTURY

• In the scientific mind, there is no such
  thing as a clean slate indeed, often quite a bit
  of erasing is required before anyone can write
  something new on the board (165).

• Biometricians view Mendels research as
  unimportant
• Broad search for Mendels Factors
• Geneticists are born.

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Thomas Hunt Morgan(1866-1945)

• First US biologist to win Nobel Prize
• Emphasis on scientific evidence and criticizes
  others for promoting ideas without evidence.
• In Evolution and Adaptation (1903), Morgan
  dismisses Darwinism for not offering satisfying
  mechanism of heredity.
• Says of Lamarckism Why not spend a small part
  of the energy, that has been used to expound the
  theory, in demonstrating that such a thing is
  really possible?

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The Fly Room
Calvin B. Bridges
A freshman washing glassware when he spotted the
first mutant fly
Co-authors of the epoch-making, revolutionary
text The Mechanism of Mendelian Inheritance
(1915)
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What About Flies in the Room?

• Morgans lab studied Drosophila melanogaster.
• Emulate de Vries large scale breeding
  experiments to improve mutation theory.
• In 6 years they observed more generations than
  Mendel and de Vries could in 2 centuries.
• After 1 year the lab spotted a recognizable
  mutation white eyes.
• Mutant bred with red eye female. All offspring
  were normal.
• Offspring inbred producing a 31 Mendel ratio for
  the recessive white eye mutation.
• Mutants fit into 4 linkage categories (based on
  the number of chromosomes they have), could be
  sex-linked, and could demonstrate strong or weak
  linkages.

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Relationship Between Chromosomes and Genes

• Morgan consults cytologist Franz Janssens.
• Janssens had observed crossing-over in meiosis.
• Morgan reasons the further apart genes are on a
  chromosome the less likely they will be linked.

Thomas Morgan. 1916. A Critique of the Theory of
Evolution
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Morgan Concludes

• Stopped short of combining mutation theory with
  selection which was hard to test in the lab
• Concluded species form by accumulated mutations
  and selection eliminates bad ones (little regard
  for gene flow or adaptation)
• Mutations were less sweeping than he expected
  but this is important too
• Paved the way for generations of geneticists

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A Return to Scientific Questions and Public
Impressions

• Flat Earth Hypothesis
• A survey of the literature reveals little hope
  for this theory
• Perspective evolution is not the only scientific
  advance to struggle against misinformation

Unfortunately, genetics cannot resolve this issue
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A Return to Scientific Questions and Public
Impressions

• Oliver the Human-zee
• After years of lively debate, Oliver's DNA was
  sampled to settle the issue and perhaps provide
  us with a breathing version of the missing link.
  The results are in ... and, alas, Oliver is just
  a standard-issue chimpanzee with a penchant for
  walking.

Genetics has helped resolve this issue!
A jump from chimpanzee to human-zee would have
pleased Morgan. But his judicious experiments
show genetics does not work with such big jumps
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Scientific Questions and Public Impressions

• The God Gene
• Hamer has expressed regret for describing THE
  God Gene
• MANY genes are required for any type of complex
  thought.
• Thought is not a round pea in classic Mendelian
  terms.
• In fact religious feelings, like all our thoughts
  and feelings, are allowed/enabled by our genes.
• Whether some are more likely to be religious
  remains open to debate in lieu of comprehensive
  research.

Geneticists continue to study this issue
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Resource to Understand Both Sides of the
Evolution-Creation Debate
http//www.evolutionminute.com
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References

• History and Biographies for Evolution
• http//www.nceas.ucsb.edu/alroy/lefa/lophodon.htm
  l
• History of Genetics
• Timeline at The Gene School http//library.thinkq
  uest.org/19037/history.html
• The Debate
• http//www.evolutionminute.com/10-graphs-charts.ht
  ml
• Sir Francis Galton
• http//www.huxley.net/contexts/index.html
• Hugo de Vries
• From a broad list of scientist biographies
  http//www.nceas.ucsb.edu/alroy/lefa/pages.html
• Mendel
• http//www.mendelweb.org/MWtoc.html
• http//evolution.berkeley.edu/evolibrary/article/0
  _0_0/history_13
• Thomas Hunt Morgan
• http//nobelprize.org/nobel_prizes/medicine/laurea
  tes/1933/morgan-bio.html
• http//evolution.berkeley.edu/evolibrary/article/0
  _0_0/history_18
• http//www.dnaftb.org/dnaftb/concept_11/con11bio.h
  tml
• Flat Earth
• http//www.sacred-texts.com/earth/za/