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Magazine Problem 7
Describe the function of the centromere. How are centromeres different from other regions of the chromosome?
Problem 15
Briefly describe the organization of genes on the chloroplast genome.
Problem 21
A diploid human cell contains approximately 6.4 billion base pairs of DNA. a. How many nucleosomes are present in such a cell? (Assume that the linker DNA encompasses 40 bp.) b. How many histone proteins are complexed with this DNA?
Problem 23
Gunter Korge examined several proteins that are secreted from the salivary glands of Drosophila melanogaster during larval development (G. Korge. 1975. Proceedings of the National Academy of Sciences of the United States of America \(72: 4550-4554\) ). One protein, called protein fraction \(4,\) was encoded by a gene found by deletion mapping to be located on the X chromosome at position 3C. Korge observed that, about 5 hours before the first synthesis of protein fraction \(4,\) an expanded and puffed-out region formed on the X chromosome at position 3C. This chromosome puff disappeared before the end of the third larval instar stage, when the synthesis of protein fraction 4 ceased. He observed that there was no puff at position \(3 \mathrm{C}\) in a special strain of flies that lacked secretion of protein fraction \(4 .\) Explain these results. What is the chromosome puff at region \(3,\) and why does its appearance and disappearance roughly coincide with the secretion of protein fraction \(4 ?\)
Problem 33
In 1979 , bones found outside Ekaterinburg, Russia, were shown to be those of Tsar Nicholas and his family, who were executed in 1918 by a Bolshevik firing squad in the Russian Revolution (see the introduction to Chapter 14 ). To prove that the skeletons were those of the royal family, mtDNA was extracted from the bone samples, amplified by PCR, and compared with mtDNA from living relatives of the tsar's family. a. Why was DNA from the mitochondria analyzed instead of nuclear DNA? What are some of the advantages of using mtDNA for this type of study? b. Mitochondrial DNA from which living relatives would provide useful information for verifying that the skeletons were those of the royal family?
