Problem #1: In 1928 Frederick Griffith conducted the
following experiment using a lethal and a nonlethal type
of pneumonia and received the following results:
2 Strains of pneumonia
Lethal (L)
Non lethal (NL)
1st Experiment
(L) + mouse = Dead Mouse
(NL) + mouse = Live Mouse
2nd Experiment
Heat-killed (L) + mouse = Live Mouse
3rd Experiment
Heat-killed (L) + (NL) + mouse = Dead Mouse
Based upon the above results, what conclusions (you
can make a list of possible conclusions) can you make to
explain the results for each experiment, especially
experiment #3?
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Possible Conclusions
1st Experiment:
2nd Experiment:
3rd Experiment:
In 1942, Oswald Avery built upon Griffith’s
experiment when designing his own procedure. He
believes that something, probably a chemical from the
nonlethal pneumonia cased the heat-killed lethal
pneumonia to change back to lethal. What chemical is
responsible for this? Below are his results:
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Griffith’s Lethal Pneumonia (L)
[(L) + chemical that destroys lipids] injected into mouse =
Dead Mouse
[(L) + chemical that destroys ribonucleic acids] injected
into mouse = Dead Mouse
[(L) + chemical that destroys carbohydrates] injected into
mouse = Dead Mouse
[(L) + chemical that destroys proteins] injected into mouse
= Dead Mouse
[(L) + chemical that destroys deoxyribonucleic acids]
injected into mouse = Live Mouse
Based upon the above experiment, what
conclusions can you formulate?
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In 1949, Erwin Chargaff separated DNA into different
chemicals. In other words, these chemicals come together
to form DNA. He came up with the following results:
Amount of Adenine = Amount of Thymine
Amount of Cytosine = Amount of Guanine
What conclusions can you determine from the above
information.
In 1953, Rosalind Franklin and Maurice Wilkins took X-rays of
crystallized DNA to determine the structure of DNA
Based upon the radiograph above, what can you determine
about the structure or appearance of DNA?
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Thomas Watson, Francis Crick, along with Wilkins and
Franklin knew that adenine and guanine are purines (
nitrogen bases made of 2 rings) and cytosine and thymine
are pyrimidines (nitrogen bases made of 1 ring).
Understanding that all of these chemicals are
components of DNA, Watson and Crick determined that
if adenine bonds to guanine and cytosine to thymine. The
structure of DNA would be crooked and lopsided. How
could you remedy this?
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