CHAPTER 2
Application and Experimental Questions
E1.
When studying living cells in a laboratory, researchers sometimes use drugs as a
way to make cells remain at a particular stage of the cell cycle. For example, aphidicolin
inhibits DNA synthesis in eukaryotic cells and causes them to remain in the G1 phase
because they cannot replicate their DNA. In what phase of the cell cycle—G1, S, G2,
prophase, metaphase, anaphase, or telophase—would you expect somatic cells to stay if
the following types of drug were added?
A.
A drug that inhibits microtubule formation
B.
A drug that allows microtubules to form but prevents them from
shortening
C.
A drug that inhibits cytokinesis
D.
A drug that prevents chromosomal condensation
Answer:
A.
G2 phase (it could not complete prophase)
B.
Metaphase (it could not enter anaphase)
C.
Telophase (it could not divide into two daughter cells)
D.
G2 phase (it could not enter prophase)
E2.
With regard to thickness and length, what do you think the chromosomes would
look like if you microscopically examined them during interphase? How would that
compare to their appearance during metaphase?
Answer: During interphase, the chromosomes are longer, thinner, and much harder to see.
In metaphase, they are highly condensed, which makes them thicker and shorter.
E3.
A rare form of dwarfism that also included hearing loss was found to run in a
particular family. It is inherited in a dominant manner. It was discovered that an affected
individual had one normal copy of chromosome 15 and one abnormal copy of
chromosome 15 that was unusually long. How would you determine if the unusually long
chromosome 15 was causing this disorder?
Answer: You could karyotype other members of the family and see if affected members
always carry the abnormal chromosome.
Questions for Student Discussion/Collaboration
1. A diploid eukaryotic cell has ten chromosomes (five per set). As a group, take turns
having one student draw the cell as it would look during a phase of mitosis, meiosis I, or
meiosis II; then have the other students guess which phase it is.
Answer: It’s not possible to give a direct answer, but the point is for students to be able
to draw chromosomes in different configurations and understand the various phases. The
chromosomes may or may not be:
1. In homologous pairs
2. Connected as sister chromatids
3. Associated in bivalents
4. Lined up in metaphase
5. Moving toward the poles.
And so on.
2. Discuss the advantages and disadvantages of sexual reproduction.
Answer: A major advantage of sexual reproduction is that it fosters genetic diversity
within future populations. A major disadvantage is that individuals of opposite sex must
find a mate.