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Question: As described in Chapter 5, not all


As described in Chapter 5, not all inherited traits are determined by nuclear genes (i.e., genes located in the cell nucleus) that are expressed during the life of an individual. In particular, maternal effect genes and mitochondrial DNA are notable exceptions. With these ideas in mind, let’s consider the cloning of a sheep (e.g., Dolly).
A. With regard to maternal effect genes, is the phenotype of such a cloned animal determined by the animal that donated the enucleated egg or by the animal that donated the somatic cell nucleus? Explain.
B. Does the cloned animal inherit extranuclear traits from the animal that donated the egg or from the animal that donated the somatic cell? Explain.
C. In what ways would you expect this cloned animal to be similar to or different from the animal that donated the somatic cell? Is it accurate to call such an animal a “clone” of the animal that donated the nucleus?



> What is cell differentiation? Discuss the role of myogenic bHLH proteins in the differentiation of muscle cells. Explain how they work at the molecular level. In your answer, explain how protein dimerization is key to gene regulation.

> Discuss the similarities and differences between the bithorax and Antennapedia complexes in Drosophila and the Hox gene complexes in mice.

> What is a heterochronic mutation? How does it affect the phenotypic outcome of an organism? What phenotypic effects would you expect if a heterochronic mutation affected the cell lineage that determines the fates of intestinal cells?

> A hypothetical cell lineage is shown here. A gene, which we will call gene X, is activated in the B-1 cell, so the B-1 cell will progress through the proper developmental stages to produce three nerve cells (D-1, D-2, and D-3) and one muscle cell (D-4).

> Cloning of mammals (such as Dolly the sheep) is described in Chapter 22. Based on your understanding of animal development, explain why an enucleated egg is needed to clone mammals. In other words, what features of the oocyte are essential for animal dev

> The arrangement of body axes of the fruit fly are shown in Figure 26.5g. Are the following statements true or false with regard to body axes in the mouse? A. Along the anteroposterior axis, the head is posterior to the tail. B.

> What is the difference between a maternal-effect gene and a zygotic gene? Of the following genes that play a role in Drosophila development, which are maternal-effect genes and which are zygotic? Explain your answer. A. nanos B. Antp C. bicoid D. lab

> Explain how loss-of-function mutations in the following categories of genes would affect the morphologies of Drosophila larvae: A. Gap genes B. Pair-rule genes C. Segment-polarity genes

> If a mutation in a homeotic gene produced the following phenotypes, would you expect it to be a loss-of-function or a gain-of function mutation? Explain your answer. A. An abdominal segment has antennae attached to it. B. The most anterior abdominal se

> Based on the photographs in Figure 26.13, in which segments is the Antp gene normally expressed? From Figure 26.13: (a) Normal fly (b) Antennapedia mutant

> Explain how an α helix in a transcription factor protein is able to function as a recognition helix.

> What would you predict to be the phenotype of a Drosophila larva whose mother was homozygous for a loss-of-function allele in the nanos gene?

> Describe the molecular features of the homeobox and homeodomain. Explain how these features are important in the function of homeotic genes.

> Discuss the role of homeotic genes in development. Explain what happens to the phenotype of a fruit fly when a gain-of-function mutation in a homeotic gene causes the protein to be expressed in an abnormal region of the embryo. What are the consequences

> With regard to development, what are the roles of the maternal effect genes versus the zygotic genes? Which types of genes are needed earlier in the development process?

> Describe the function of the Bicoid protein. Explain how its ability to exert its effects in a concentration-dependent manner is a critical feature of its function.

> Discuss how the anterior portion of the anteroposterior axis is established in Drosophila. What aspects of oogenesis are critical in establishing this axis? What do you think would happen if the bicoid mRNA was not trapped at the anterior end but instead

> What four types of cellular processes must occur to enable a fertilized egg to develop into an adult multicellular animal? Briefly discuss the role of each process.

> Explain the difference between gene modification and gene addition. Are the following examples of gene modification or gene addition? A. A mouse model to study cystic fibrosis B. Introduction of a pesticide-resistance gene into corn using the T-DNA vec

> When comparing (i.e., aligning) two or more genetic sequences, it is sometimes necessary to put in gaps. Explain why. Discuss two changes (i.e., two types of mutations) that could happen during the evolution of homologous genes that would explain the occ

> What is the difference between similarity and homology?

> Which of these mechanisms is the most energy-efficient way to regulate gene expression? From figure 15.1: REGULATION OF GENE EXPRESSION Gene Regulatory transcription factors can activate or inhibit transoription. The arrangements and composition of

> A multiple-sequence alignment of five homologous proteins is shown here: Discuss some of the interesting features that this alignment reveals. 50 1 MLAFLNOVRK PTLDLPLEVR RKMWFKP FM. OSYLVVFIGY LTMYLIRKNF 2 MLAFLNOVRK PILDLALDVR RKMWFKP FM. OSYLVVFIG

> Discuss the distinction between sequence recognition and pattern recognition.

> Besides the examples listed in Table 24.3, list five types of short sequences that a geneticist might want to locate within a DNA sequence.

> Which of the following examples is likely to be caused by a somatic mutation? A. A purple flower has a small patch of white tissue. B. One child, in a family of seven, is an albino. C. One apple tree, in a very large orchard, produces its apples 2 wee

> What is a database? What types of information are stored within a database? Where does the information come from? Discuss the objectives of a genome database.

> An individual carries a somatic mutation that changes a lysine codon into a glutamic acid codon. Prior to acquiring this mutation, the individual had been exposed to UV light, proflavin, and 5-bromouracil. Which of these three agents would be the most li

> In the treatment of cancer, the basis for many types of chemotherapy and radiation therapy is that mutagens are more effective at killing dividing cells than nondividing cells. Explain why. What are possible harmful side effects of chemotherapy and radia

> A segment of DNA has the following sequence: TTGGATGCTG AACCTACGAC A. What would the sequence be immediately after reaction with nitrous acid? Let the letters H represent hypoxanthine and U represent uracil. B. Let’s suppose this DNA was reacted with n

> What is the difference between an autonomous and a nonautonomous transposable element? Is it possible for nonautonomous TEs to move? If yes, explain how. 

> The occurrence of multiple transposons within the genome of organisms has been suggested as a possible cause of chromosomal rearrangements such as deletions, translocations, and inversions. How could the occurrence of transposons promote these types of s

> How does micF antisense RNA affect the translation of ompF mRNA?

> What features distinguish a transposon from a retrotransposon? How are their sequences different, and how are their mechanisms of transposition different?

> This chapter describes different types of TEs, including insertion elements, simple transposons, LTR retrotransposons, and non-LTR retrotransposons. Which of these four types of TEs have the following features? A. Require reverse transcriptase to transp

> Let’s suppose that a species of mosquito has two different types of simple transposons that we will call X elements and Z elements. The X elements appear quite stable. In a population of 100 mosquitoes, it is found that every mosquito has 6 X elements, a

> Do you consider TEs to be mutagens? Explain.

> Which types of TEs have the greatest potential for proliferation: insertion elements, simple transposons, or retrotransposons? Explain your choice

> Discuss the reasons why the proteome is larger than the genome of a given species.

> Why does transposition always produce direct repeats in the chromosomal DNA?

> For insertion elements and simple transposons, what is the function of the inverted repeat sequences during transposition?

> If you were examining a sequence of chromosomal DNA, what characteristics would cause you to believe that the sequence contained a transposable element?

> According to the scenario shown in Figure 20.7, how many segments of DNA (one, two, or three) are removed during site-specific recombination within the gene that encodes the κ (kappa) light chain for IgG proteins? How many segments are splice

> Explain how the presence of tryptophan favors the formation of the 3–4 stem-loop.

> Describe the functions of the RAG1 and RAG2 and NHEJ proteins.

> Briefly describe three ways that antibody diversity is increased

> What type of DNA structure is recognized by RecG and RuvABC? Do you think these proteins recognize DNA sequences? Be specific about what type(s) of molecular recognition these proteins can perform.

> Discuss the concerns that some people have with regard to the uses of genetically engineered organisms.

> Discuss some of the worthwhile traits that can be modified in transgenic plants.

> Give the meanings of the following terms: genomics, functional genomics, and proteomics.

> Ehler-Danlos syndrome is a rare disorder caused by a mutation in a gene that encodes a protein called collagen (type 3 A1). Collagen is found in the extracellular matrix that plays an important role in the formation of skin, joints, and other connective

> Gaucher disease (type I) is due to a defect in a gene that encodes a protein called acid β-glucosidase. This enzyme plays a role in carbohydrate metabolism within lysosomes. The gene is located on the long arm of chromosome 1. People who inherit two defe

> Discuss why a genetic disease might have a particular age of onset. Would an infectious disease have an age of onset? Explain why or why not.

> What type of bonding interaction causes stem-loops to form?

> Figure 25.1 illustrates albinism in two different species. Describe two other genetic disorders found in both humans and animals. From Figure 25.1:

> We often speak of diseases such as phenylketonuria (PKU) and achondroplasia as having a genetic basis. Explain whether the following statements are accurate with regard to the genetic basis of any human disease (not just PKU and achondroplasia). A. An i

> In general, why do changes in chromosome structure or number tend to affect an individual’s phenotype? Explain why some changes in chromosome structure, such as reciprocal translocations, do not.

> Many genetic disorders exhibit locus heterogeneity. Define and give two examples of locus heterogeneity. How does locus heterogeneity confound a pedigree analysis?

> When the DNA of a human cell becomes damaged, the p53 gene is activated. What is the general function of the p53 protein? Is it an enzyme, transcription factor, cell-cycle protein, or something else? Describe three ways in which the synthesis of the p53

> With regard to cancer cells, which of the following statements are true? A. Cancer cells are clonal, which means they are derived from a single mutant cell. B. To become cancerous, cells usually accumulate multiple genetic changes that eventually resul

> A p53 knockout mouse in which both copies of p53 are defective has been produced by researchers. This type of mouse appears normal at birth. However, it is highly sensitive to UV light. Based on your knowledge of p53, explain the normal appearance at bir

> The rb gene encodes a protein that inhibits E2F, a transcription factor that activates several genes involved in cell division. Mutations in rb are associated with certain forms of cancer, such as retinoblastoma. Under each of the following conditions, w

> Relatively few inherited forms of cancer involve the inheritance of mutant oncogenes. Instead, most inherited forms of cancer are defects in tumor-suppressor genes. Give two or more reasons why inherited forms of cancer seldom involve activated oncogenes

> A genetic predisposition to developing cancer is usually inherited as a dominant trait. At the level of cellular function, are the alleles involved actually dominant? Explain why some individuals who have inherited these dominant alleles do not develop c

> How does tryptophan affect the function of trp repressor?

> A genetic predisposition to developing cancer is usually inherited as a dominant trait. At the level of cellular function, are the alleles involved actually dominant? Explain why some individuals who have inherited these dominant alleles do not develop c

> What is a retroviral oncogene? Is it necessary for viral infection and proliferation? How have retroviruses acquired oncogenes?

> What is a proto-oncogene? What are the typical functions of proteins encoded by proto-oncogenes? At the level of protein function, what are the general ways that proto-oncogenes can be converted to oncogenes?

> What is the difference between an oncogene and a tumor-suppressor gene? Give two examples of each type of gene.

> Explain, at the molecular level, why human genetic diseases often follow a simple Mendelian pattern of inheritance, whereas most normal traits, such as the shape of your nose or the size of your head, are governed by multiple gene interactions.

> Some people have a genetic predisposition for developing prion diseases. Examples are described in Table 25.6. In the case of Gerstmann-Straüssler-Scheinker disease, the age of onset is typically 30–50 years, and the dura

> What is a prion? Explain how a prion relies on normal cellular proteins to cause a disease such as mad cow disease.

> What is the purpose of the International HapMap Project? How will it help researchers who study disease-causing alleles?

> Describe the two assumptions that underlie the identification of disease-causing alleles via haplotypes.

> Sandhoff disease is due to a mutation in a gene that encodes a protein called hexosaminidase B. This disease has symptoms that are similar to those of Tay-Sachs disease. Weakness begins in the first 6 months of life. Individuals exhibit early blindness a

> Which data provide the strongest evidence that O1 is not the only operator site?

> Marfan syndrome is due to a mutation in a gene that encodes a protein called fibrillin-1. It is inherited as a dominant trait. The fibrillin-1 protein is the main constituent of extracellular microfibrils. These microfibrils can exist as individual fiber

> Lesch-Nyhan syndrome is due to a mutation in a gene that encodes a protein called hypoxanthine-guanine phosphoribosyltransferase (HPRT). HPRT is an enzyme that functions in purine metabolism. People afflicted with this syndrome have severe neurodegenerat

> Achondroplasia is a rare form of dwarfism caused by an autosomal dominant mutation that affects the gene that encodes a fibroblast growth factor receptor. Among 1,422,000 live births, the number of babies born with achondroplasia was 31. Among those 31 b

> Like Hurler syndrome, Fabry disease involves an abnormal accumulation of substances within lysosomes. However, the lysosomes of individuals with Fabry disease show an abnormal accumulation of lipids. The defective enzyme is α-galactosidase A, which is a

> Hurler syndrome is due to a mutation in a gene that encodes a protein called α-l-iduronidase. This protein functions within lysosomes as an enzyme that breaks down mucopolysaccharides (a type of polysaccharide that has many acidic groups at

> With regard to pedigree analysis, make a list of observations that distinguish recessive, dominant, and X-linked patterns of inheritance.

> What part of the A. tumefaciens DNA gets transferred to the genome of a plant cell during infection?

> What is a transgenic organism? Describe three examples.

> What is a mouse model for human disease?

> As shown in Table 22.2, several medical agents are now commercially produced by genetically engineered microorganisms. Discuss the advantages and disadvantages of making these agents this way. From Table 22.2: Examples of Medical Agents Produced by

> Why is it beneficial for the bacterium to regulate the lac operon with both a repressor protein and an activator protein?

> Which is more common anagenesis or cladogenesis?

> In a strain of mice, the average 6-week body weight is 25 g, and the narrow-sense heritability for this trait is 0.21. A. What would be the average weight of the offspring if parents with a mean weight of 27 g were chosen? B. What parental mean weight

> The average thorax length in a Drosophila population is 1.01 mm. You want to practice selective breeding to make larger Drosophila. To do so, you choose 10 parents (5 males and 5 females) of the following sizes: 0.97, 0.99, 1.05, 1.06, 1.03, 1.21, 1.22,

> In a wild strain of tomato plants, the phenotypic variance for tomato weight is 3.2 g2. In another strain of highly inbred tomatoes raised under the same environmental conditions, the phenotypic variance is 2.2 g2. With regard to the wild strain, A. Est

> Outline the steps you would follow to determine the number of genes that influence the yield of rice. Describe the results you might get if rice yield is governed by variation in six different genes.

> Let’s suppose that two strains of pigs differ in 500 RFLPs. One strain is much larger than the other. The pigs are crossed to each other, and the members of the F1 generation are also crossed among themselves to produce an F2 generation. Three distinct R

> From an experimental viewpoint, what does it mean to say that an RFLP is associated with a trait? Let’s suppose that two strains of pea plants differ in two RFLPs that are linked to two genes governing pea size. RFLP-1 is found in 2000-bp and 2700-bp ban

> You conduct an RFLP analysis of head weight in one strain of cabbage; you determine that seven QTLs affect this trait. In another strain of cabbage, you find that only four QTLs affect this trait. Note that both strains of cabbage are from the same speci

> The abdomen length (in millimeters) was measured in 15 male Drosophila, and the following data were obtained: 1.9, 2.4, 2.1, 2.0, 2.2, 2.4, 1.7, 1.8, 2.0, 2.0, 2.3, 2.1, 1.6, 2.3, and 2.2. Calculate the mean, standard deviation, and variance for this pop

> The trait of blood pressure in humans has a frequency distribution that is similar to a normal distribution. The following graph shows the ranges of blood pressures for a selected population of people. The red line depicts the frequency distribution of t

> An animal breeder had a herd of sheep with a mean weight of 254 pounds at 3 years of age. He chose animals with a mean weight of 281 pounds as parents for the next generation. When these offspring reached 3 years of age, their mean weight was 269 pounds.

> Under what conditions is lac repressor bound to the lac operon?

> For each of the following relationships, correlation coefficients for height were determined for 15 pairs of individuals: Mother-daughter: 0.36 Mother-granddaughter: 0.17 Sister-sister: 0.39 Sister-sister (fraternal twins): 0.40 Sister-sister (identi

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