Chapter 7 Nucleic Acids: The Molecular Basis of Life • MHR 249COMMUNICATING30.Draw a diagram that illustrates the hydrogen
bonds that occur between two different base
pairs of DNA. Why is base pairing so specific?
31.Create a table that contrasts the structure and
function of DNA and RNA.
32.Develop a flowchart that illustrates how the
discoveries of the following researchers
contributed to an understanding of the role of
DNA in heredity: Hershey and Chase; Chargaff;
Franklin and Wilkins; Watson and Crick;
Meselson and Stahl.
33.Imagine a conversation between Phoebus
Levene and Erwin Chargaff about the role
played by nucleic acids in heredity. What
evidence might each researcher rely on to
support his point of view?
34.DNA is sometimes said to be like a language.
In a short essay, explain the ways in which
this comparison is valid.
35.“DNA replication involves a careful balancing
act.” Prepare a poster demonstration that could
be used to explain what this statement means.
36.What examples can you provide from everyday
life that could be used to illustrate the concepts
of conservative, semi-conservative, and
dispersive replication?MAKING CONNECTIONS37.In his work on patterns of inheritance,
Gregor Mendel coined the term “factors of
inheritance.” How do Mendel’s factors relate
to today’s definition of a gene?
38.Only a small portion of the mammalian
genome is made up of genes. The rest was
originally referred to as “junk DNA.” How do
popular terms such as this help or hinder
society’s understanding of the need for
scientific procedures and ongoing research?
What are some of the potential advantages and
disadvantages to an organism of having large
quantities of non-gene DNA?
39.A certain planarian has a genome 6000 times
larger than that of a particular yeast cell.
(a)What conclusions, if any, could you draw
about the relative complexities of the two
organisms?
(b)What practical applications could there be
from a study that compared the genomes of
the two organisms?
40.A researcher develops a form of DNA
polymerase that adds nucleotides only to the
5 ′hydroxyl group of an existing DNA strand.
Is this a useful discovery? Explain.pathway for valine in this bacteria includes
the following steps: precursor A →precursor
B →valine.
(a)What might you conclude about the mutant
bacteria?
(b)How would you design an experiment to
test your hypothesis?
(c)Could a similar experiment be used if you
were studying a plant cell rather than a
bacterium? Explain.27.A biochemist develops a chemical that
interferes with histone-histone bonding.
What effect would you expect this chemical
to have on the following:
(a)the organization of DNA within a
prokaryotic cell?
(b)the organization of DNA within a
eukaryotic cell?
(c)the process of replication of eukaryotic DNA?
28.Examine the photograph at right, taken by an
electron microscope.
(a)What events and processes are taking place
in this image?
(b)Make an illustration showing what you
would expect to see if a second photograph
were taken a short time after this one.29.During cell division in a eukaryotic cell,
replication can be simultaneously initiated in
thousands of places along a single linear
chromosome. Propose a mechanism that the
cell could use to ensure that each portion of
the chromosome is only replicated once during
any given round of cell division.