328 MHR • Unit 3 Molecular Genetics
COMMUNICATING46.In 1943, 10 years before Watson and Crick
published their paper on the structure of DNA,
the atomic physicist Erwin Schrödinger
predicted that the secret to life would be traced
to the interactions among molecules within a
larger, crystal-like compound. With a partner,
discuss this prediction. Then prepare a debate
for presentation to your class in which you
take opposing sides to argue the ways in which
you believe Schrödinger was right on the one
hand and wrong on the other. You should each
conclude your arguments with a single sentence
that reflects your most important point.
47.Your community is hosting a series of public
information meetings about health issues. The
objective of the series is to teach people about
the science behind healthy lifestyle choices. You
are asked to make a 10-minute presentation on
the topic “DNA and Mutations.”
(a)Write a one- or two-sentence key message
you would want your audience to remember.(b)Outline your presentation under five main
headings, beginning with “Introduction”
and ending with “Conclusion.”
(c)Under each heading list three points you
would want to cover and describe each in
a few sentences.
48.During a conversation with your neighbour, he
emphatically states, “The cloning of human
cells is a barbaric practice that should be banned
immediately.” Assuming your neighbour has
no background in genetics, how would you
respond? What information in support of your
point of view would you provide?
49.As a teaching tool, imagine that a prokaryotic
cell and a eukaryotic cell meet on a microscope
slide and have an argument about which of
them does a better job of regulating gene
expression. Write a short exchange of dialogue
between them that covers three points each cell
might make to your class.
50.You are part of a team involved in creating
genetically modified crops that can grow inOrdinarily, the mRNA strand begins with the
triplet AUG occupying nucleotide positions
1, 2, and 3 along the strand and codes for a
protein 12 amino acids long. The table shows
the results obtained when each of the tainted
samples is placed in a suspension containing
amino acids and the enzymes necessary for
protein synthesis.After considering these results, answer the
following questions.
(a)Which of the samples could contain
the following mutation? Explain your
reasoning. (You may wish to refer to the
genetic code table on page 254.)
(i)UAA in position 6–8
(ii)UAA in position 16–18
(iii)UAA in position 26–28
(b)Further testing shows that your reasoning
was incorrect. For each sample, suggest
what additional factors might affect the
results you expected.44.In humans, brown eyes occur when cells in the
iris produce the protein melanin, while blue
eyes occur when melanin is not produced.
(a)Write a hypothesis that could explain, in
terms of gene expression, why brown eyes
are dominant and blue eyes are recessive.
(b)Design an experiment you could conduct to
test your hypothesis. What would you use
as a control?
(c)An individual who carries one gene for blue
eyes and one gene for brown eyes may still
have eyes that are as dark as those of an
individual who carries two genes for brown
eyes. Explain, in terms of the regulation of
gene expression, how this is possible. Use
a diagram to illustrate your explanation.
45.A bacterial cell that has been exposed to high
levels of X rays soon afterward begins to produce
enormous quantities of many different types of
polypeptides, very few of which are the normal,
functional proteins it usually produces.
(a)What kind of mutation could account for
this effect?
(b)Assume the mutation has no other effect on
gene expression. If your hypothesis about
the cause of the mutation is correct, what
other observation(s) about the polypeptide
products would you expect to make?Sample Observations
A
B
Cno functional protein product
fully functional protein product
slightly altered but generally functional protein product