Chapter 18 Developmental Genetics1) Which term refers to the regulatory events that establish a specific pattern of gene activity and developmental fate for a given cell?A) lysogenB) differentiationC) determinationD) gradient regulatedE) attenuationAnswer: CSection: Introduction, 18.12) Which general genetic process is believed to account for the variety of cellular structures and functions in eukaryotic cells?A) variable gene activityB) negative control exclusivelyC) maternal environmental activitiesD) intron processingE) RNA processingAnswer: ASection: 18.13) Immediately after fertilization of a Drosophila egg, the zygote nucleus undergoes a series of divisions. Subsequent nuclear migration generates a(n) ________.A) syncytial blastodermB) maternal effectC) homeodomainD) zygoteE) cleavage nucleusAnswer: ASection: 18.34) In Drosophila, the sequential order of the function of segmentation genes is ________.A) gap, segment-polarity, pair-ruleB) pair-rule, transdeterminal, gapC) transdeterminal, gap, pair-ruleD) gap, pair-rule, segment-polarityE) segmentational, helical, sphericalAnswer: DSection: 18.41Copyright © 2012 Pearson Education, Inc.5) Mutations that eliminate a contiguous region in the Drosophila embryo's segmentation pattern are called ________.A) homeodomainsB) gap genesC) compartment genesD) linkage genesE) segment genesAnswer: BSection: 18.46) Which of the following is a fundamental characteristic of the Notch pathway?A) It works through nuclear signals involving the lac operon.B) It works through direct cell to cell contact.C) It allows mRNAs to accumulate in the posterior portion of the Drosophila embryo.D) It directs mRNAs to antisense systems in the posterior portion of all organisms.E) It provides symmetry to plant flowers.Answer: BSection: 18.77) Provide an explanation of the differences between differentiation and determination. Provide examples of each process and indicate how each is involved in development.Answer: Determination is the early commitment of a cell to an eventual developmental fate. Differentiation is the set of functional and structural changes associated with the expression of that developmental fate. When nuclei of the developing Drosophila embryo reach the blastodermstage, they become determined. Differentiation of the cells in Drosophila occurs during metamorphosis. Development, therefore, probably depends first on the determination of cells, then on the differentiation of cells.Section: Introduction, 18.18) How does determination relate temporally to differentiation?Answer: Determination occurs when a cell's developmental fate is set, whereas differentiation is the expression of that determined state. Determination occurs before differentiation.Section: Introduction9) Define determination and differentiation.Answer: Determination is the early commitment of a cell to an eventual developmental fate. Differentiation is the set of functional and structural changes associated with the expression of that developmental fate.Section: Introduction, 18.12Copyright © 2012 Pearson Education, Inc.10) Maternal effects are cases of extrachromosomal inheritance in which the genotype of the mother influences the phenotype of her immediate offspring in a non-Mendelian manner. Providea rationale for the molecular basis of a maternal effect.Answer: During development of the egg, females provide numerous nutritional and informational substances, which direct and support early embryonic development. These substances are often in the form of transcription factors, receptors, mRNA, and proteins, although other substances are also likely (substrates and products). In some cases, these maternally supplied substances override the actual genotype of the zygote and produce a phenotype much like the genotype of the mother.Section: 18.3, 18.411) Provide a brief description of the variable gene activity hypothesis as it relates to development. What information is often provided in support of this hypothesis?Answer: Since all cells apparently have the same genetic information, yet may differ structurallyand functionally, the variable gene activity hypothesis suggests that differential gene transcription (genetic regulation) accounts for such cellular diversity. Evidence in support of this model includes the following: chromosome puffs, isozymes, and the presence of genes but no gene products in some tissues (hemoglobin, for example).Section: 18.112) Design an experiment that would allow you to determine if a particular nucleus in a Drosophila embryo is capable of directing development of an entire new fly.Answer: Experiments in support of such genomic equivalence include the following: the observation that chromosome number and structure do not consistently change in different cells of an organism, nuclear transplantation in amphibians, and the presence of genes but no gene products in some tissues (hemoglobin, for example). The cloning of Dolly also supports the above. For the Drosophila experiment, one could do nuclear transplantation similar to the classicexperiments in amphibians and recent experiments in mammals or transplant a cell from embryos of one genotype to the posterior end of the early embryos of another genotype. The transplanted cells would be reprogrammed into germ cells by the posterior P granules. The transplant can be detected in the next generation by the recognizable different phenotypes due to different genotypes of the donor and recipient. Section: 18.113) Experiments involving nuclear transplantation in amphibians indicate that nuclei derived from blastula are more likely to support development of complete and normal adults compared with those derived from later stages of development. What do these experiments tell us about the process of development?Answer: Development occurs as a series of cascades, with early genes influencing late genes, at times with stability. Such progressive determination, if stable, may be irreversible and fail to support development of an entire organism from a single cell. A number of epigenetic factors such as chromatin remodeling and DNA methylation are also likely to come into play.Section: 18.1, 18.43Copyright © 2012 Pearson Education, Inc.14) Which functions earlier in development: maternal-effect genes or zygotic genes?Answer: maternal-effect genesSection: 18.3, 18.415) A gene that specifies the fate of a particular anatomical segment in Drosophila is called a(n) ________.Answer: