Chapter 7 Review Questions:
1. Please name and describe two general methods by which the human cell uses to
fit a large genome into a small nucleus.
2. How many total types of chromosomes are present in the human genome? Are
the number of chromosome types different for each gender? Please explain your
answer for both questions.
3. How many genes are present in the human genome? Is this an unexpectedly large
or small number? Please explain your answer.
4. How many copies of each chromosome does each individual have? How does this
fit with the number of copies of genes each individual has?
5. How many copies of each gene are present on a chromosome?
6. Please state why the human genome needs to be packaged.
7. Below is the picture of a chromosome. Please appropriately label all the
important components. Additionally, please state where the origins of replication
are located, and explain why the origins are located there. Please describe the
functions of all the components labeled.
8. An individual has Achondroplasia, one of the common causes of dwarfism in
humans. This disorder is caused by a mutation in the FGFR3 gene, which is on the
very end of the p-arm on chromosome 4. This mutation results in a change in DNA
sequence at base 1138 in which a guanine (in the normal) to an adenine (in the
mutant). There are two variations of the FGFR3 gene in the population
F= variation with adenine
f= variation with the guanine
Please draw pictures of each copy of chromosome 4 for the genotype(s) that result
in achondroplasia.
9. Why do organisms need to wind their DNA? What class of proteins are necessary
for DNA winding? Please name them all.
10. Which proteins are present in the core nucleosome? Please discuss how the core
nucleosome forms in detail. Please include when and how much DNA winds.
11. How many base pairs of DNA are wound around the core nucleosome? How
many base pairs of DNA are wound around the entire nucleosome?
12. Does the nucleosome have an axis of symmetry? If so, please explain accurately
where the symmetry lies as well as well as where the DNA enters and exits the
nucleosome.
13. What characteristic of nucleosome structure allows for the bending and winding
of DNA? If you wanted to unwind the DNA, how would you counteract this
“characteristic?”
14. Where within the DNA structure do the histone proteins bind the DNA? Please
explain in 1 sentence why the histone proteins bind there.
15. Please discuss the selenoid vs. the zig-zag model of chromatin structure. Which
is physiologically relevant? Why (Please be detailed in your answer)?
16. Please list and explain the three methods the cell uses after dividing the genome
into chromosomes, to compact the DNA into the cell nucleus. Within your answer
please discuss the TOTAL compaction after each method.
17. Please predict the appropriate conformation for the 30 nm fiber in the
organisms below (Please note that less than 40 bp of linker DNA is considered
short).
1. Oak Tree: 130 bp of linker DNA
2. Mouse: 43 bp of linker DNA
3. S. pombe (fission yeast): 12 bp of linker DNA
4. Drosophila: 34 bp of linker DNA
5. Elephant 76 bp of linker DNA
6. Shark 52 bp of linker DNA
18. You are performing an experiment to determine the amount of DNA wound
around the nucleosomes of the following organisms. Which enzyme would you use
and why? Based on the data below, please state your conclusions, including how
much DNA is protected by Histone H1.
a. Coyote-low concentration: bands in multiples of 177 bp
Coyote- high concentration: single band at 141 bp
b. Human-low concentration: bands in multiples of 180 bp
Human-high concentration: single band at 147 bp
c. Lion- low concentration: bands in multiples of 164 bp
Lion-high concentration: single band at 126 bp
19. You wish to do an experiment in which you determine the amount of DNA
wound around both a core nucleosome, as well as the total nucleosome. Which
experiment would you perform, and why?
20. Please describe in detail how histone acetylation affects chromatin winding. In
the process of your description, please include the enzymes that are responsible for
changing histone acetylation states.
21. You are interested in studying expression of the FBN1 gene which is implicated
in Marfan’s syndrome gene. Upon examination of your expression data from a
normal healthy person you find that the FBN1 gene is expressed to the following
levels in each cell type:
a. epidermal cell: low
b. neuron: high
c. muscle cell: high
d. kerotinocyte: high
e. vascular endothelial cell: high
f. pancreatic cell: low
Please state which type of chromatin your gene should be found in for each cell type.
22. Which type of chromatin takes up more volume within the nucleus? In which
type of chromatin is most of the DNA found? Please explain why your answers for
each question are the same or different.
23. Please list three different methods by which the cell can modify chromatin
structure, and briefly describe how they do this.