Genetics: A Conceptual Approach

Benjamin Pierce

Chapter 11 Chromosome Structure and Organelle DNA - all with Video Answers

Educators

Chapter Questions

01:36

Problem 1

How does supercoiling arise? What is the difference between positive and negative supercoiling?

Jessica Wooten

Numerade Educator

01:32

Problem 2

What functions does supercoiling serve for the cell?

Jessica Wooten

Numerade Educator

01:59

Problem 3

Describe the composition and structure of the nucleosome

Jessica Wooten

Numerade Educator

03:44

Problem 4

Describe in steps how the double helix of DNA, which is $2 \mathrm{nm}$ in width, gives rise to a chromosome that is 700 nm in width.

Jessica Wooten

Numerade Educator

01:53

Problem 5

What are polytene chromosomes and chromosomal puffs?

Malya Arula Halimun

Numerade Educator

02:18

Problem 6

What are epigenet ic changes and how are they brought about?

Malya Arula Halimun

Numerade Educator

01:46

Problem 7

Describe the function of the centromere. How are centromeres different from other regions of the chromosome?

Jessica Wooten

Numerade Educator

02:21

Problem 8

Describe the function and molecular structure of a telomere.

Jessica Wooten

Numerade Educator

01:48

Problem 9

What is the difference between euchromatin and heterochromatin?

Jessica Wooten

Numerade Educator

00:25

Problem 10

What is the C value of an organism?

Jessica Wooten

Numerade Educator

04:40

Problem 11

Describe the different dasses of DNA sequence variation that exist in eukaryotes.

Malya Arula Halimun

Numerade Educator

03:35

Problem 12

Explain why many traits encoded by mtDNA and œDNA exhibit considerable variation in their expression, even among members of the same family.

Khalida Dawar

Numerade Educator

03:14

Problem 13

What is the endosymbiotic theory? How does it help to explain some of the characterist ics of mitochondria and chlomplasts?

Bryan Valdivia

Numerade Educator

03:27

Problem 14

What evidence supports the endosymbiotic theory?

Jessica Wooten

Numerade Educator

02:17

Problem 15

Briefly describe the organization of genes on the chloroplast genome.

Khalida Dawar

Numerade Educator

00:20

Problem 16

What is meant by the term "promiscuous DNA"?

Jessica Wooten

Numerade Educator

02:56

The introduction to this chapter discussed a study of telomere length in Romanian children. The study demonstrated that children raised in orphanages had shorter telomeres than children raised in foster homes. What effect, if any, do you think having shorter telomeres in childhood might have on adult life?

Jessica Wooten

Numerade Educator

01:57

Problem 18

Compare and contrast prokaryotic and eukaryotic chromosomes. How are they alike and how do they differ?

Jessica Wooten

Numerade Educator

02:31

Problem 19

(a) In a typical eukaryotic cell, would you expect to find more molecules of the H1 histone or more molecules of the H2A histone? Fxplain your reasoning. (b) Would you expect to find more molecules of H2A or more molecules of H3? Explain your reasoning.

Sirisa Reddy

Numerade Educator

04:36

Problem 20

20. Based on the DNA sensitivity to DNase I illustrated in Figure $11.7,$ which type of chicken hemoglobin (embryonic or adult) is likely produced in highest quantity at the following tissues and developmental stages?
a. Eryth roblasts during the first 24 hours.
b. Eryth roblasts at day 5
c. Erythroblasts at day 14
d. Brain cells throughout development

Khalida Dawar

Numerade Educator

01:33

Problem 21

Suppose that a researcher briefly added radioactively labeled uridine to the Drosophila larva whose polytene chromosome is shown in Figure $11.6 .$ Label on the figure where you would expect to see accumulation of radioactive uridine.

Khalida Dawar

Numerade Educator

03:09

Problem 22

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 $40 \mathrm{bp.}$ )
b. How many histone proteins are complexed to this DNA?

Jessica Wooten

Numerade Educator

03:44

Problem 23

Would you expect to see more or less acetylation in regions of DNA that are sensitive to digest ion by DNase I? Why?

Khalida Dawar

Numerade Educator

01:25

Problem 24

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 $3 \mathrm{C}$. Korge obs erved 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 $3 \mathrm{C}$. 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 $4 ?$

Khalida Dawar

Numerade Educator

03:10

Problem 25

Suppose a chemist develops a new drug that neutralizes the positive charges on the tails of histone proteins. What would be the most likely effect of this new drug on chromatin structure? Would this drug have any effect on gene expression? Explain your answers.

Jessica Wooten

Numerade Educator

01:48

Problem 26

Which of the following two molecules of DNA has the lower melting temperature? Why?

Jessica Wooten

Numerade Educator

03:38

Problem 27

In a DNA hybridization study, DNA was isolated from a particular species, labeled with $^{32} \mathrm{P}$, and sheared into small fragments (S. K. Dutta et al. 1967. Genetics $57: 719-727$ ). Hybridizations between these labeled fragments and denatured DNA from different species were then compared. The following table gives the percentages of labeled wheat DNA that hybridized to DNA molecules of wheat, corn, radish, and cabbage.
Percentage of bound wheat DNA
$\begin{array}{lc}\text { Species } & \text { hybridized relative to wheat } \\ \text { Wheat } & 100 \\ \text { Cabbage } & 23 \\ \text { Corn } & 63 \\ \text { Radish } & 30\end{array}$
What do these results indicate about the evolutionary differences among these organisms?

Khalida Dawar

Numerade Educator

View

Problem 28

A wheat plant that is light green in color is found growing in a field. Biochemical analysis reveals that chloroplasts in this plant produce only $50 \%$ of the chlorophyll normally found in wheat chloroplasts. Propose a set of crosses to determine whether the light-green phenotype is caused by a mutation in a nuclear gene or in a chloroplast gene.

Jessica Wooten

Numerade Educator

01:44

Problem 29

A rare neurological disease is found in the family illustrated in the following pedigree. What is the most likely mode of inheritance for this disorder? Explain your reasoning.

Khalida Dawar

Numerade Educator

02:09

Problem 30

Assume that the disonder shown in the pedigree in the Worked Problem on $p .313$ is a rare disease that results from a defect in mitochrondrial DNA. If individual III- 8 has a daughter, what is the probability that the daughter will inherit the muscle disonder from her affected parent?

Khalida Dawar

Numerade Educator

05:39

Problem 31

Fredrick Wilson and his colleagues studied members of a large family who had low levels of magnesium in their blood (see the pedigree below). They argued that this disorder of magnesium (and associated high blood pressure and high cholesterol) is caused by a mutation in mtDNA (F. H. Wilson et al. 2004. Science 306:1190-1194).
a. What evidence suggests that a gene in the mtDNA is causing this disorder?
b. Could this disorder be caused by an aut osomal dominant gene? Why or why not?

Khalida Dawar

Numerade Educator

01:28

Problem 32

In a particular strain of Neurospora, a poky mutation exhibits biparental inheritance, whereas poky mutations in other strains are inherited only from the maternal parent. Explain these results.

Jessica Wooten

Numerade Educator

03:36

Problem 33

A scientist collects cells at various points in the cell cyde and isolates DNA from them. Using density-gradient centrifugation, she separates the nuclear and mtDNA. She then measures the amount of mtDNA and nuclear DNA present at different points in the cell cycle. On the following graph, draw a line to represent the relative amounts of nuclear DNA that you expect her to find per cell throughout the cell cycle. Then, draw a dotted line on the same graph to indicate the relative amount of mt DNA that you would expect to see at different points throughout the cell cycle.

Khalida Dawar

Numerade Educator

02:53

Problem 34

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, mt DNA 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 nudear DNA? What are some of the advantages of using mtDNA for this type of study?
b. Mitochrondrial DNA from which living relatives would provide useful information for verifying that the skeletons were those of the royal family?

Khalida Dawar

Numerade Educator

02:57

Problem 35

Antibiotics such as chloramphenicol, tetracycline, and erythromycin inhibit protein synt hesis in eubacteria but have no effect on protein synthesis encoded by nuclear genes. Cycloheximide inh ibits protein synthesis encoded by nuclear genes but has no effect on eubacterial protein synthesis. How might these compounds be used to determine which proteins are encoded by mitochondrial and chloroplast genomes?

Khalida Dawar

Numerade Educator

02:08

Problem 36

An explorer discovers a strange new species of plant and sends some of the plant tissue to a geneticist to study. The geneticist isolates chromatin from the plant and examines it with an electron microscope. She observes what appear to be beads on a string. She then adds a small amount of nuclease, which cleaves the string into individual beads that each contain 280 bp of DNA. After digestion with more nuclease, a 120 -bp fragment of DNA remains attached to a core of histone proteins. Analysis of the histone core reveals histones in the following proportions:
On the basis of these observations, what conclusions could the geneticist make about the probable structure of the nucleosome in the chromatin of this plant?

Khalida Dawar

Numerade Educator

04:48

Problem 37

In DNA-hybridization experiments on six species of plants in the genus Vicia, DNA was isolated from each of the six species, denatured by heating, and sheared into small fragments (W. Y. Chock. 1971. Genctics 68.213-230). In one experiment, DNA from each species and from $E$ coli was allowed to renature. The graph shows the results of this renaturation experiment.
$1=V$. melanops, $2-V$ sativa, $3=V$, benghalensis.
$4=V$ atropurpurea, $5-V .$ faba, $6-V$, narbonensis, $7=E .$ coll
a. Can you explain why the $E$. coli DNA renatures at a much faster rate than does DNA from all of the Vicia species?
b. Notice that, for the Vicia species, the rate of renaturation is much faster in the first hour and then slows down. What might cause this init ial rapid renaturation and the subsequent slowdown?

Khalida Dawar

Numerade Educator

01:40

Problem 38

Steven Frank and Laurence Hurst argued that a cytoplasmically inherited mutation in humans that has severe effects in males but no effect in females will not be eliminated from a population by natural selection. because only females pass on mtDNA (S. A. Frank and L. D. Hurst. 1996. Nature 383: 224 ). Using this argument, explain why males with Leber hereditary optic neuropathy are more severely affected than females.

Jessica Wooten

Numerade Educator

04:13

Problem 39

In a study of a myopathy, several families exhibited vision problems, musde weakness, and deafness (M. Zeviani etal. 1990. American burnal of Human Genetics $47.904-914$ ). Analysis of the mtDNA from affected penons in these families revealed that large numbers of their mtDNA possessed deletions of varying length. Different members of the same family and even different mitochondria from the same person possessed deletions of different sizes; so the underlying defect appeared to be a tendency for the mitDNA of affected persons to have deletions. A pedigree of one of the families studied is shown here. The researchers conchided that this disorder is inherited as an autosomal dominant trait and they mapped the disease-causing gene to a position on chromosome 10 in the nucleus.
a. What characteristics of the pedigree rule out inheritance of a trait encoded by a gene in the mtDNA?
b. Explain how a mutation in a nuclear gene might lead to deletions in mtDNA.

Khalida Dawar

Numerade Educator

01:16

Problem 40

Mitochondrial DNA sequences have been detected in the nuclear genomes of many organisms, and cpDNA sequences are sometimes found in the mitochondrial genome. Propose a mechanism for how such "promiscuous DNA" might move between nuclear, mitochondrial, and chloroplast genomes.

Jessica Wooten

Numerade Educator

Problem 1

Problem 2

Problem 3

Problem 4

Problem 5

Problem 6

Problem 7

Problem 8

Problem 9

Problem 10

Problem 11

Problem 12

Problem 13

Problem 14

Problem 15

Problem 16

Problem 17

Problem 18

Problem 19

Problem 20

Problem 21

Problem 22

Problem 23

Problem 24

Problem 25

Problem 26

Problem 27

Problem 28

Problem 29

Problem 30

Problem 31

Problem 32

Problem 33

Problem 34

Problem 35

Problem 36

Problem 37

Problem 38

Problem 39

Problem 40