Chapter 12 DNA Organization in Chromosomes1) Viral chromosomes exist in a variety of conformations and can be made up of ________.A) protein- or lipid-coding sequencesB) DNA onlyC) DNA or RNAD) RNA onlyE) DNA, RNA, or proteinAnswer: CSection: 12.12) In E. coli, the genetic material is composed of ________.A) circular, double-stranded DNAB) linear, double-stranded DNAC) RNA and proteinD) circular, double-stranded RNAE) polypeptide chainsAnswer: ASection: 12.13) Eukaryotic chromosomes contain two general domains that relate to the degree of condensation. These two regions are ________.A) called heterochromatin and euchromatinB) uniform in the genetic information they containC) separated by large stretches of repetitive DNAD) each void of typical protein-coding sequences of DNAE) void of intronsAnswer: ASection: 11.44) In human chromosomes, satellite DNA sequences of about 170 base pairs in length are presentin tandem arrays of up to 1 million base pairs. Found mainly in centromere regions, these DNA sequences are called ________.A) telomeresB) primersC) alphoid familiesD) euchromatic regionsE) telomere-associated sequencesAnswer: CSection: 12.61Copyright © 2012 Pearson Education, Inc.5) In addition to highly repetitive and unique DNA sequences, a third category of DNA sequences exists. What is it called, and what types of elements are involved in it?A) composite DNA; telomeres and heterochromatinB) dominant DNA; euchromatin and heterochromatinC) multiple gene family DNA; hemoglobin and 5.0S RNAD) moderately repetitive DNA; SINEs, LINEs, and VNTRsE) permissive DNA; centromeres and heterochromatinAnswer: DSection: 12.66) Chromatin of eukaryotes is organized into repeating interactions with protein octomers called nucleosomes. Nucleosomes are composed of which class of molecules?A) histonesB) glycoproteinsC) lipidsD) H1 histonesE) nonhistone chromosomal proteinsAnswer: ASection: 12.47) That some organisms contain much larger amounts of DNA than are apparently "needed" and that some relatively closely related organisms may have vastly different amounts of DNA is more typical in ________.A) viruses than in bacteriaB) RNA viruses than in DNA virusesC) eukaryotes than in prokaryotesD) the alphoid rather than the diphloid familyE) prokaryotes than in eukaryotesAnswer: CSection: 12.4, 12.68) Although mutations have been observed in many different genes, they have not been isolated in histones. Why does this seem reasonable? If one wanted to produce antibodies to histones, would it be an easy task? Explain your answer.Answer: Histones represent one of the most conserved molecules in nature because they are involved in a fundamental and important function relating to chromosome structure. Mutations are probably lethal. Since all antibody-producing organisms have essentially the same histones, itwould be difficult to find an organism that produces histone antibodies, for to do so would be self-destructive.Section: 12.49) What is unusual about the amino acid composition of histones? How is the function of histones related to the amino acid composition? Of which histones are nucleosomes composed?Answer: Histones contain large amounts of positively charged amino acids such as lysine and arginine. Thus, they can bind electrostatically to the negatively charged phosphate groups of nucleotides. Nucleosomes are composed of all histones except H1.Section: 12.42Copyright © 2012 Pearson Education, Inc.10) Describe the basic structure of a nucleosome. What is the role of histone H1?Answer: Nucleosomes are composed of four different histone molecules, each of which exists twice, thus forming an octomer. Histone H1 is between nucleosomes and is associated with linker DNA.Section: 12.411) Which portion of a chromosome is typically stained when chromosome preparations are heat denatured and then treated with Giesma stain?Answer: centromeric regionsSection: 12.512) Compare and contrast the chromosome structure of viruses, bacteria, and eukaryotes.Answer: The amount of DNA per structure (virus particle, bacterium, cell) increases as one goesfrom viruses to eukaryotic cells. Viral chromosomes may be composed of single-stranded or double-stranded RNA or DNA, whereas bacterial and eukaryotic DNA is double-stranded. Bacterial DNA is considered to be a covalently closed circle; the "global" structure of eukaryotic chromosomes is uncertain. Although some proteins are associated with viral and bacterial DNA, the regularly spaced histones of eukaryotic chromosomes are unique.Section: 12.1,12.413) A particular variant of the lambda bacteriophage has a DNA double-stranded genome of 51,365 base pairs. How long would this DNA be?Answer: One base pair is 0.34 nm; therefore: 51,365 bp × 0.34 nm/bp = 17,464 nm or 17.46 μm.Section: 12.114) List the components of a nucleosome.Answer: Histones H2A, H2B, H3, and H4 exist as two types of tetramers: (H2A)2 + (H2B)2 and(H3)2 + (H4)2.Section: 12.415) List several configurations that characterize different viral chromosomes.Answer: DNA (single- and double-stranded), RNA (single- and double-stranded), linear, circularSection: 12.116) In instances in the eukaryotic genome, DNA sequences represent evolutionary vestiges of duplicated copies of genes. What are such regions called and what are their characteristics?Answer: Pseudogenes are duplicated copies of genes that have undergone considerable mutationand share some homology to the original gene.Section: 12.717) What are minisatellites and microsatellites?Answer: Both are highly repetitive, relatively short DNA sequences.Section: 12.63Copyright © 2012 Pearson Education, Inc.18) Describe the chromosomal conformations of φX174 and polyoma viruses.Answer: single-stranded DNA, circular; double-stranded DNA, circular, respectivelySection: 12.119) What similarities do bacterial chromosomes have with eukaryotic chromosomes?Answer: Both have double-stranded DNA and several types of proteins associated with that DNA (nucleosomes in eukaryotes and HU and H1 proteins in bacteria).Section: 12.1, 12,2, 12.420) How does a polytene chromosome differ from a typical eukaryotic chromosome?Answer: Polytene chromosomes are found in a variety of tissues in the larvae of some flies and several species of protozoans and plants. A polytene chromosome contains banding patterns and is large because of repeated replications of DNA without nuclear division.Section: 12.321) What are histones, and how are they