280 MHR • Unit 3 Molecular Genetics
SECTION REVIEW- Explain why gene regulation in bacteria is
(a)more likely to take place at the level of mRNA
transcription than after translation; and
(b)unlikely to involve stopping protein synthesis
between transcription and translation. - Write a short sentence to distinguish between
the following pairs.
(a)gene and operon
(b)transcriptional control and translational control
(c)promoter and operator - List three ways in which the process of gene
regulation differs between prokaryotic and eukaryotic
cells. - Explain how the arrangement of DNA in a
eukaryotic cell affects
(a)the availability of DNA for transcription;
(b)the rate of transcription of DNA to pre-mRNA; and
(c)the number of different mRNA transcripts that
can be produced from a single stretch of DNA. - A red blood cell contains no nucleus, but it
can synthesize new hemoglobin molecules during
its lifetime.
(a)How is this possible?
(b)Considering that the mRNA coding for hemoglobin
in a red blood cell has an unusually long poly-A
tail, what might be this feature’s significance?
(c)How might this principle be applied in other
medical settings? List up to three possibilities
and explain your choices.- Positive gene regulation, negative gene regulation,
inducer, repressor, and co-repressor are terms that
can be confusing. Prepare a series of flash cards that
can be used to help understand these terms. - While working with a particular strain of E. coli,
you discover that it transcribes the lacgenes at a
high level when no lactose is present in the cell’s
medium. List the possible causes of this activity.
Then design an experiment to determine which of
these possible causes is the case with your
bacterial colony.
All cancers arise because of changes to the process of
protein synthesis in living cells. As part of your research,
look for articles or other information sources that describe
the genes involved in these changes and the polypeptides
for which they code. Note any ways in which the cancer
you are studying relates to changes in transcription or
translation.UNIT PROJECT PREP
ICMCK/UK/UK/UK/Uto their destinations outside the cell (that is, to
elsewhere in the organism). The result in both
cases is that post-translational control is achieved
— the polypeptide product is broken down without
ever becoming a functional protein.
In Chapter 7, you saw that the earliest theories of
genetics held that DNA was not sufficiently complex
to encode hereditary information. Scientists such
as Levene concluded that this role must belong to
proteins, and that DNA could be just a structural
component of chromosomes. In the middle of the
twentieth century, this theory was reversed. In
other words, researchers concluded that DNA was
the genetic material and proteins played only a
secondary role. Since then, scientists have learned
more about the role of proteins in regulating gene
expression. The evidence available today suggests
that the truth lies somewhere in between these two
earlier models. DNA contains the information of
heredity. However, by determining when and how
that information is expressed, proteins play an
equally important role in deciding the nature of life.The more scientists learn about the interaction
between DNA and proteins, the more they are
able to manipulate living cells. In the next chapter,
you will learn about some of the new genetic
technologies that have given researchers the ability to
change the expression of genes in living organisms,
and even to design entirely new organisms.http://www.mcgrawhill.ca/links/biology 12
DNA is required to synthesize proteins, but DNA itself would
not exist without the proteins needed to synthesize nucleic
acids, replicate DNA, transcribe mRNA, and translate genetic
information into polypeptides. Which came first? The more
scientists learn about the interaction between DNA and
proteins, the more questions they raise about how life may
have originated. Use the Internet to research some of the
theories on how nucleic acids first came into being. What are
some of the practical applications of this research? To discover
more, go to the web site above, and click on Web Links.