Download 34 Solved Questions on Regulatory Proteins - Exam 2 | BIO 5620 and more Exams Developmental biology in PDF only on Docsity!
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MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Questions 1 - 31 are each worth 3 points.
- The illustration on the right shows the concentration gradient of transcription factor X, ie., how far factor X travels within the embryo. Transcription factor X also happens to be a morphogen in a syncytial embryo. The illustration on the left shows the genes that are turned on in specific compartments of the embryo. Among the given choices, deduce the most correct conclusions in questions 1 and 2.
Based on the illustrations above, the relative order of binding affinities (where ʺ>ʺ means a higher affinity) to morphogen X by the promoter regions of the following genes is most likely: A) R > S > T B) U > S > T C) R > S > U D) U > S > R
- Which of the following statement(s) might be true based on the illustrations shown above in question 1?
A) Gene A is expressed in the indicated compartments because gene Aʹs expression can be inhibited by the morphogen B) Gene T is expressed in the indicated compartment because gene Tʹs expression can be inhibited by protein R C) Gene U is expressed in the indicated compartment because gene Uʹs expression can be inhibited by protein S D) Two of the above E) All of the above
- A Drosophila embryo has gain-of-function mutations in both cactus and toll , where both proteins are now always active. Which of the phenotypes below would you expect for the double mutant embryo? A) a normal embryo B) a dorsalized embryo that lacks ventral structures C) a ventralized embryo that lacks dorsal structures
- During gastrulation in Drosophila , part of the endoderm is formed from A) cells that invaginate from the ventral furrow of the embryo B) cells that invaginate from the anterior region of the embryo C) All of the above D) None of the above
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- Panel A shows the expression patterns of the regulatory proteins within the wild-type embryo, which has 4 segments (seg 1 - 4). The anterior and posterior ends of the embryo are indicated.
Panel B shows the DNA fragment that can bind the indicated proteins that regulate the expression of the target gene. Both activator 1 and activator 2 are required to act together to drive the expression of the target gene. Either repressor 1 or repressor 2 is sufficient to inhibit the expresion of the target gene.
However, a mutant embryo has acquired a mutation where repressor 1 can no longer bind to its regulatory element. Which of the following would be the expected expression of the target gene after the said mutation?
A) B)
C) D) None of the above
- Certain mRNAs are localized to different compartments of the Drosophila oocyte through association with A) microfilaments via kinesin or dynein proteins B) microtubules via kinesin or dynein proteins C) intermediate filaments via kinesin or dynein proteins D) Two of the above E) All of the above
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- Below is an image of a wild-type Drosophila embryo. Gene A specifies the identities of segments 2, 4 and 6 of the embryo, whereas gene B specifies the denticle hairs in the anterior compartment of each segment of the embryo. Which of the following statements might be true based on this information?
A) Loss-of-function mutations in gene A leads to completely naked embryos (without denticle hairs), because gene A is an example of a segment - polarity gene B) Loss-of-function mutations in gene B leads to completely naked embryos (without denticle hairs), because gene B is an example of a segment-polarity gene C) Loss-of-function mutations in gene A leads to completely naked embryos (without denticle hairs), because gene A is an example of a pair-rule gene D) Loss-of-function mutations in gene B leads to completely naked embryos (without denticle hairs), because gene B is an example of a pair-rule gene E) None of the above
- In a wild-type mammal, Hox gene A specifies the cervical vertebrae, while Hox genes C and D specify the first and second thoracic vertebrae, respectively. On the other hand, Hox genes B and E specify the lumbar vertebrae. In the mutant mammal, the first lumbar vertebrae have acquired thoracic-like features. Among the given choices, deduce the most correct conclusions in questions 10 and 11.
In the wild type, the relative order of expression of the Hox genes will be A) A > B > C > D > E, where A is expressed first, B is expressed second, C is expressed third and E is expressed last B) E > D > C > B > A, where E is expressed first, D is expressed second, C is expressed third and A is expressed last C) A > C > D > B > E, where A is expressed first, C is expressed second, D is expressed third and E is expressed last D) E > B > D > C > A, where E is expressed first, B is expressed second, D is expressed third and A is expressed last
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- Which of the following statement(s) might be true based on the illustrations shown above in question 10? A) The mutant has acquired homeotic transformations B) The Wnt morphogen gradient along the anteroposterior axis of the mutant has been altered C) The FGF morphogen gradient along the anteroposterior axis of the mutant has been altered D) Two of the above E) All of the above
- Which of the following mutations could give rise to a dorsalized Drosophila early embryo, i.e., an embryo that lacks any ventral structures?
A) A FLP/FRT-induced loss-of-function mutation in the torpedo gene of the dorsal follicle cells, but not in the torpedo gene of other cells B) A FLP/FRT-induced gain-of-function mutation in the torpedo gene of the dorsal follicle cells, but not in the torpedo gene of other cells. The gain-of-function mutation causes Torpedo to be active independent of its ligand. C) A FLP/FRT-induced loss-of-function mutation in the torpedo gene of the ventral follicle cells, but not in the torpedo gene of other cells D) A FLP/FRT-induced gain-of-function mutation in the torpedo gene of the ventral follicle cells, but not in the torpedo gene of other cells. The gain-of-function mutation causes Torpedo to be active independent of its ligand. E) A FLP/FRT-induced loss-of-function mutation in the torpedo gene of oocytes, but not in the torpedo gene of other cells
- Which of the following mutations could give rise to a ventralized mammalian neural tube, i.e. , a neural tube that lacks any dorsal structures? A) A loss-of-function mutation in Gli only in the dorsal cells of the neural tube B) A loss-of-function mutation in Chordin only in the dorsal cells of the neural tube C) A gain-of-function mutation in Patched, where it is always active only in the ventral cells of the neural tube D) A gain-of-function mutation in SMADs, where they are always active only in the dorsal cells of the neural tube E) None of the above
- Which of the following mutations could give rise to a dorsalized mammalian neural tube, i.e. , a neural tube that lacks any ventral structures? A) A loss-of-function mutation in Gli only in the dorsal cells of the neural tube B) A loss-of-function mutation in Chordin only in the dorsal cells of the neural tube C) A gain-of-function mutation in Patched, where it is always active only in the ventral cells of the neural tube D) A gain-of-function mutation in SMADs, where they are always active only in the dorsal cells of the neural tube E) None of the above
- The specification of the anteroposterior axis of the mammalian embryo involves signals from: A) extraembryonic cells B) embryonic cells C) All of the above D) None of the above
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- Sperm entry in: A) both the amphibian Xenopus oocyte and the fly Drosophila oocyte will specify the future ventral side of the animals B) the fly Drosophila oocyte is fixed and occurs through the micropyle C) the amphibian Xenopus oocyte is fixed and occurs through a micropyle-like structure D) Two of the above E) All of the above
- Which statement would most likely be true? A) Paralogs are homologous genes that resulted from gene duplication within the genome of a single species B) Paralogs are homologous genes with similar functions, which are present in different species and have descended from a common ancestor C) All of the above D) None of the above
- Which statement would most likely be true? A) Transcription in the amphibian Xenopus and in mammals start at the mid-blastula transition B) Transcription in the amphibian Xenopus starts at the mid-blastula transition, whereas mammalian transcription starts before the mid-blastula transition C) Transcription in the amphibian Xenopus starts at the mid-blastula transition, whereas mammalian transcription starts after the mid-blastula transition D) Transcription in the amphibian Xenopus and in mammals start before the mid-blastula transition E) Transcription in the amphibian Xenopus and in mammals start after the mid-blastula transition
- Which statement would most likely be true? A) Both the amphibian Xenopus egg and the Drosophila egg are activated at fertilization B) Both the amphibian Xenopus egg and the Drosophila egg are activated before fertilization C) The amphibian Xenopus egg is activated at fertilization, whereas the Drosophila egg is activated before fertilization D) The amphibian Xenopus egg is activated before fertilization, whereas the Drosophila egg is activated at fertilization
- Which of the following mutation(s) could give rise to a dorsalized mammalian neural tube, i.e. , a neural tube that lacks ventral structures? A) An embryo that carries a loss-of-function mutation in Shh only in the notochord cells B) An embryo that carries a loss-of-function mutation in BMP only in the notochord cells C) An embryo that carries a loss-of-function mutation in Shh in the notochord cells, but a gain-of-function mutation in Shh in the floor plate cells of the neural tube, where the Shh protein is always active D) An embryo that carries a loss-of-function mutation in BMP in the notochord cells, but a gain-of-function mutation in Shh in the floor plate cells of the neural tube, where the Shh protein is always active
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- Which statement would most likely be true? A) The notochord and neural crest cells are derived from the ectoderm B) The notochord is derived from the ectoderm and the neural crest cells are derived from the mesoderm C) The notochord is derived from the mesoderm and the neural crest cells are derived from the ectoderm D) The notochord and neural crest cells are derived from the mesoderm E) None of the above
- Which statement would most likely be true? A) Epidermal fusion and neural tube closure during neurulation requires heterotypic interactions between cadherins, where the epidermis expresses E-cadherin and the neural plate expresses N-cadherin B) Epidermal fusion requires homotypic interactions between cadherins, where the epidermal tissue expresses N-cadherin at one end and E-cadherin on the other end C) Epidermal fusion and neural tube closure during neurulation requires homotypic interactions between cadherins, where the epidermis expresses E-cadherin and the neural plate expresses N-cadherin D) Neural tube closure requires heterotypic interactions between cadherins, where the neural plate expresses N-cadherin at the anterior end and E-cadherin at the posterior end E) None of the above
- Which statement(s) would most likely be true?
A) The amphibian Xenopus blastopore is analogous to the mammalian primitive streak B) The amphibian Xenopus Spemann-Mangold organizer is analogous to the mammalian primitive streak C) The amphibian Xenopus blastopore is analogous to the mammalian node D) Two of the above E) All of the above
- Which statement(s) would most likely be true? A) BMP signaling is involved in patterning the dorsal-ventral axis of the Drosophila embryo B) BMP signaling is involved in patterning the dorsal-ventral axis of the Xenopus embryo C) BMP signaling is involved in patterning the dorsal-ventral axis of a mammalian embryo D) Two of the above E) All of the above
- Which statement would most likely be true? A) Autonomus specification is cell specification that is dependent on signals from other cells B) Conditional specification is cell specification that is independent of signals from other cells C) Conditional specification is non-autonomous specification D) Two of the above E) All of the above
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SHORT ANSWERS. Write your answers within the space provided.
- A gain-of-function hypermorphic mutation in gene A leads to an embryo with extra limbs, whereas a loss-of-function mutation in gene B or gene C leads to an embryo with no limbs. However, an embryo carrying a loss-of-function mutation in gene A and a gain-of-function hypermorphic mutation in gene C has no limbs, while an embryo carrying a gain-of-function hypermorphic mutation in gene A and a loss-of-function mutation in gene B also has no limbs. In addition, an embryo carrying a gain - of-function hypermorphic mutation in gene C and a loss-of-function mutation in gene B has no limbs.
From the information given, draw a possible pathway that would best depict the interactions between genes A, B and C, if they are acting within a linear pathway. (5 points)
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- Name the different classes of segmentation genes that pattern the anterior-posterior axis of the Drosophila embryo_._ List them according to the correct temporal order in which they activate each other, where the first gene class activated is listed first. (2 points)
BONUS QUESTION (1 point)
- Team 1 presented the Ogden et al Nature 2008 paper on Feb 11, 2016. What is the hypothesis of the paper?
