CHAPTER 12
Questions for Student Discussion/Collaboration
1.
Bacterial and eukaryotic chromosomes are very compact. Discuss the advantages
and disadvantages of having a compact structure.
Answer: You need to have the DNA compact to fit in the cell. Compaction allows a cell to
store more information. Without this ability, organisms would not have been able to evolve
to the high levels of complexity they have achieved. The down side is that cells need to copy
and access this information. Therefore, cells need to make the structure looser. To achieve
both goals, the structure of chromosomes is extremely dynamic.
2.
The prevalence of highly repetitive sequences seems rather strange to many
geneticists. Do they seem strange to you? Why or why not? Discuss whether or not you
think they have an important function.
Answer: This is a matter of opinion. It seems strange to have so much DNA that seems to
have no obvious function. It's a waste of energy. Perhaps it has a function that we don’t
know about yet. On the other hand, evolution does allow bad things to accumulate within
genomes such as genes that cause diseases, etc. Perhaps this is just another example of the
negative consequences of evolution.
3.
Discuss and make a list of the similarities and differences between bacterial and
eukaryotic chromosomes.
Answer: The DNA structure is the same, except the degree of supercoiling. The protein
compositions are very different. Bacteria compact their chromosomes by supercoiling
and looping. Eukaryotes wrap their DNA around histones to form nucleosomes. The
nucleosomes associate with one another to form looped fibers and these fibers are
supported on a scaffold.