Lecture 18: Eukaryotic Genomic Organization, Chromosomes
1. What is chromatin and what are its major structural components?
2. What is a nucleosome and what are its major components.
3. Describe the successive levels of compaction that must occur to compress an extended double helical DNA sufficiently to fit in a condensed mitotic chromosome.
4. What is heterochromatin and what is its significance?
5. Describe some of the ways in which chromosome banding patterns have been employed in research on human genetics.
6. What roles are played by centromeres and telomeres?
7. Distinguish between introns and exons in a manner that makes it clear you know what each is and how they differ.
8. What is meant by a multigene family, and how is it believed to have originated during evolution?
9. Would you expect the diploid genome of a human male to contain the same amount of DNA as the diploid genome of a human female? Explain your answer. (Note that you can obtain some rather precise data from the web page whose link is included in the lecture 18 notes).
10. The web page cited in the lecture 18 notes claims that human chromosome 1 contains 263 Mb of DNA. If you were using a wire that was 2.0 mm in diameter as a model of that DNA, how long would it be? (Hint: A DNA double helix is approximately 2 nm in diameter, with each base pair approximately 0.34 nm thick. Convert your answer to miles (one kilometer = 0.621 miles).
11. What is the range of sizes of eukaryotic genomes? How many fold difference is there between the smallest and the largest? How do the extremes of the range of sizes compare with the size of the human genome?
12. Briefly explain how the position of the centromere on a chromosome is used to classify types of chromosomes.
13. What is a polytene chromosome and what importance does it have in the study of genetics?
14. Distinguish between the p and q arms of an acrocentric chromosome in a manner that makes it clear you know what each is and how they differ.
15. Briefly identify and explain each of the following.
a. C-value paradox
b. FISH (acronym)
c. Sister chromatids
d. Histone
e. Pseudogene.
15. Distinguish between the following pairs in a manner that makes it clear you know what each is and how they differ.
a. Repititive and unique sequence DNA
b. Heterochromatin and euchromatin
c. Acrocentric and telocentric chromosomes.
d. Kinetochore and centromere
e. Karyotype and genome
16. Yeast artificial chromosomes (YACs) are widely used as vectors.
a. What advantages do YACs offer relative to most other types of vectors?
b. What are the minimum characteristics that a YAC must possess.
c. Describe the plasmid form of a YAC that is maintained in a bacterial cell prior to cloning the DNA insert.
d. Would you expect a typical cloned DNA insert carried in a YAC to contain a cut site for Eco RI? Explain the reasoning behind your answer.
e. Describe a procedure for selective growth of yeast cells that have taken up a YAC,
17. Sickle cell anemia is caused by a point mutation in the beta-globin gene. What mechanisms prevent homozygosity for the sickle cell allele from having serious effects on the developing fetus prior to birth? (See figure 10.27 if you are having trouble with this question.)
18. Distinguish between a processed pseudogene and an unrpocessed pseudogene. What are the major characteristics of each?
19. Roughly how much of the human genome is believed to consist of protein-coding genes? What does the rest consist of?
20. Under what conditions do chromosomes exist as single unpaired chromatids. Why is it that they are so seldom depicted in that state?
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