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Dr. Stuart Reichler
Bio 325
Sample Exam Questions:
Some organisms have much more DNA than
humans do. Does this mean that they can
make a greater diversity of proteins than
humans can? Why or why not?
Sample Exam Questions:
Some organisms have much more DNA than
humans do. Does this mean that they can
make a greater diversity of proteins than
humans can? Why or why not?
Not necessarily. They may have more noncoding DNA.
Sample Exam Questions:
If a transposon was inserted into an intron,
would the gene product still be properly
produced? Why or why not?
Sample Exam Questions:
If a transposon was inserted into an intron,
would the gene product still be properly
produced? Why or why not?
Either: Yes, the intron will be spliced out
along with the transposon thereby having no
effect on the final mRNA. No, the transposon
will disrupt proper splicing of the intron
thereby causing the mRNA to have additional
and improper sequence.
Sample Exam Questions:
What is a major weakness of the data obtained
via microarray analysis?
Sample Exam Questions:
What is a major weakness of the data obtained
via microarray analysis?
Microarrays show differences in mRNA levels,
but that does not necessarily correlate to
changes in protein levels.
Studying Biology:
•Start with a question.
–For example:
How? Why? When? Where? Etc?
•How do we get answers?
–Strong Inference presents one method
(article on webpage)
Cause of Peptic
Ulcers:
Overabundance of
stomach acid due to
•Stress
•Diet
•Anxiety
Cause of Peptic
Ulcers:
Overabundance of
stomach acid due to
•Stress
•Diet
•Anxiety
Treatment:
•Antiacid
U.S. bought
$4.4 billion in 1992
•Tranquilizers
Dr. Barry Marshall
The real cause
of 80% of
ulcers…
H. pylori
The obvious or accepted answer was not the
correct answer...
Without alternative ideas, the answer would
not have been found.
Strong Inference
Knowledge is gained by eliminating
incorrect ideas.
Disproof is more reliable than proof.
Where does the
matter come
from for plants
to grow?
Matter can not
normally be created
or destroyed, only
moved from one
place to another.
Aristotle (~2,300 y.a.):
Plants gain mass by taking it
from the soil.
Supporting Evidence:
•Plants need soil to grow.
•If roots are removed, plants die.
•After several years of cultivation, soil loses its
ability to support plant growth.
Johann Baptista van Helmont
did a simple experiment in
the early 1600’s
What is the major difference between these two
approaches to science?
Johann Baptista van Helmont
Aristotle (~2,300 y.a.):
Plants gain mass by taking it in 1600’s
from the soil…
Supporting Evidence:
• Plants need soil to grow.
• If roots are removed,
plants die.
• After several years of
cultivation, soil loses its
ability to support plant
growth.
The Rules of Strong Inference:
Strong Inference is a method for looking at scientific
problems by trying to disprove hypotheses and
accepting the hypotheses that can not be disproved.
Using Strong Inference entails following these rules
(from an article by John Platt, 1964):
1. Devise multiple hypotheses.
The Rules of Strong Inference:
Strong Inference is a method for looking at scientific
problems by trying to disprove hypotheses and
accepting the hypotheses that can not be disproved.
Using Strong Inference entails following these rules
(from an article by John Platt, 1964):
1. Devise multiple hypotheses.
2. Design experiment(s) to eliminate one or more of
the hypotheses.
The Rules of Strong Inference:
1. Devise multiple hypotheses.
2. Design experiment(s) to eliminate one or more of
the hypotheses.
3. Carry out the experiments in a manner that gives a
clean result.
What experimental
errors might this
experiment have?
Johann Baptista van Helmont
did a simple experiment in
the early 1600’s
The Rules of Strong Inference:
1. Devise multiple hypotheses.
2. Design experiment(s) to eliminate one or more of
the hypotheses.
3. Carry out the experiments in a manner that gives a
clean result.
4. Repeat. Refine hypotheses.
The Rules of Strong Inference:
Strong Inference is a method for looking at scientific problems
by trying to disprove hypotheses and accepting the hypotheses
that can not be disproved. Using Strong Inference entails
following these rules (from an article by John Platt, 1964):
1. Devise multiple hypotheses.
2. Design experiment(s) to eliminate one or more of the
hypotheses.
3. Carry out the experiments in a manner that gives a clean
result.
4. Repeat. Refine hypotheses.
The Rules of Strong Inference:
Strong Inference is a method for looking at scientific problems
by trying to disprove hypotheses and accepting the hypotheses
that can not be disproved. Using Strong Inference entails
following these rules (from an article by John Platt, 1964):
1. Devise multiple hypotheses.
2. Design experiment(s) to eliminate one or more of the
hypotheses.
3. Carry out the experiments in a manner that gives a clean
result.
4. Repeat. Refine hypotheses.
The Questions:
•Can your hypothesis be disproved?
•What experiment(s) can disprove your
hypothesis?
The Rules of Strong Inference:
Strong Inference is a method for looking at scientific problems
by trying to disprove hypotheses and accepting the hypotheses
that can not be disproved. Using Strong Inference entails
following these rules (from an article by John Platt, 1964):
1. Devise multiple hypotheses.
2. Design experiment(s) to eliminate one or more of the
hypotheses.
3. Carry out the experiments in a manner that gives a clean
result.
4. Repeat. Refine hypotheses.
What causes Mad Cow Disease (aka BSE)?
Brain tissue from cow with BSE. Scrapie in
sheep, CJD or Kuru in humans looks similar.
Is Mad Cow Disease (BSE) transmissible?
How could you test for the infectious agent?
Dr. Stanley Prusiner
was awarded the
Nobel Prize in 1997
for the discovery of
prions… infectious
proteins.
normally folded proteins
Prion
(abnormally
folded
protein)
Prion
Propogation
Interaction
between prion
and normal
protein causes
normal protein
to misfold…
… which leads to
increasing numbers
of prions
Scientists communicate by publishing their
findings in journals…