694 Chapter 20 NEL
Section 20.4 Questions
- Clearly define the following terms and give an example of
each: mutation, frameshift mutation, point mutation,
nonsense mutation, missense mutation.
2.Explain why mutations, such as insertions or deletions, are
often much more harmful than nitrogen-base substitutions.
3.Which of two types of mutations, nonsense or missense,
would be more harmful to an organism? Explain your
answer using your knowledge of protein synthesis.
4.Identify three factors that can produce gene mutations.
5.Identify the type of mutation that has occurred in the
strands below. Describe the effect on the protein. The
original strand is
AUG UUU UUG CCU UAU CAU CGU
Determine whether or not the following mutations would
be harmful to an organism. Translate the mRNA sequence
into protein to help you decide. The mutation is indicated
in red.
(a) AUG UUU UUG CCU UAU CAU CGU
AUG UUU UUG CCU UACCAU CGU
(b) AUG UUU UUG CCU UAU CAU CGU
AUG UUU UUG CCU UAA CAU CGU
(c) AUG UUU UUG CCU UAU CAU CGU
AUG UUU CUU GCC UUA UCA UCG U
(d) AUG UUU UUG CCU UAU CAU CGU
AUG UUU UUG CCU AUC AUC GU
(e) AUG UUU UUG CCU UAU CAU CGU
UGC UAC UAU UCC GUU UUU GUA
6.Which of the following amino acid changes can result from
a single base-pair substitution?
(a) arg to leu
(b) cys to glu
(c) ser to thr
(d) ile to ser - Explain why a food dye that has been identified as a
chemical mutagen poses greater dangers for a developing
fetus than for an adult.
8.List three changes that can be made to your personal
lifestyle that would reduce the odds of a mutation taking
place.
9.Explain how mutations may be of benefit to an organism,
and describe how these beneficial mutations are maintained
in a species. Identify the biological process that influences
which mutations stay in a population over time.
10.Both mitochondria and chloroplasts contain their own
genomes, which are separate from the nuclear genome. The
DNA in mitochondria and chloroplasts have been used as
evidence for the endosymbiotic theory of the evolution of
eukaryotic organisms. This theory was developed by the
American scientist Dr. Lynn Margulis. According to this
theory, mitochondria and chloroplast arose from bacteria
and algae cells that became engulfed by another cell with
which they had a symbiotic relationship. Over time, the
bacteria and algae became a part of the other cell. Evidence
of this theory can be found by comparing the DNA of
mitochondria with bacteria, and of chloroplasts with algae.
Go to the Nelson Web site to learn more about the theory of
endosymbiosis, and summarize the DNA evidence that
supports it.Extension- The mutation that causes sickle cell anemia involves the
substitution of the amino acid valine for the amino acid
glutamic acid. Research the structure of valine and
glutamic acid and, with your knowledge of chemistry,
hypothesize why this substitution results in a large
conformational change for the hemoglobin protein. List
other amino acids that could have been substituted instead
of valine that may not have caused such serious side
effects. List amino acids that are similar to glutamic acid
that would probably cause similar side effects.
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