Exam 2 with Answer Key - Developmental Biology Honors | BIO 5620, Exams of Developmental biology

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Exam 2

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3. Either activator 1, activator 2 or activator 3 is sufficient to drive the expression of the target gene, whereas either repressor 1 or repressor 2 can inhibit the expression of the target gene.

The expression patterns of the different regulatory proteins are shown below. The DNA fragment that binds the indicated proteins that regulate the expression of the target gene is also shown below.

However, the target gene regulatory element has now acquired a mutation, where repressor 1 can no longer bind to it. Which of the following would be the expected expression of the target gene after the said mutation in the regulatory DNA fragment?

A) B)

C) D)

4. Non-autonomous signaling is illustrated by: A) Notch signaling B) the activity of the Spemann-Mangold organizer C) cell specification during the C. elegans two-cell stage D) Two of the above E) All of the above

Exam 2

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9. The illustration on the left shows the concentration gradient of a morphogen that happens to be a transcription factor. The illustration on the right shows the specific genes that are turned on in specific compartments of the syncytial embryo. Among the given choices, deduce the most correct conclusions in questions 6 and 7.

A) Gene X is only transcribed in the compartment that is exposed to the highest morphogen concentration, because gene Xʹs recognition elements have the highest affinity for the morphogen, when compared to the recognition elements found in genes Y and Z B) Gene Z is transcribed in the different compartments shown, because gene Zʹs recognition elements have the highest affinity for the morphogen, when compared to the recognition elements found in genes X and Y C) Gene X is transcribed in only one compartment, because the products of genes Y and Z inhibit gene X expression D) Two of the above E) All of the above

10. Which of the following statement(s) might be true based on the illustrations shown above in question 6? A) Gene B is expressed in the indicated compartment because gene B can be inhibited by the morphogen and by gene A B) Gene A is expressed in the indicated compartment because gene A can be inhibited by gene B and by the morphogen C) All of the above D) None of the above

11. Anteroposterior axis specification in the Drosophila embryo: A) is initiated after fertilization B) requires that any mRNA should be localized specifically either at the anterior end or the posterior end of the egg C) is coordinated with dorsoventral axis specification D) Two of the above E) All of the above

Exam 2

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12. If Hox gene 1 specifically determines the identity of rhombomere 1, whereas Hox gene 2 specifically determines the identity of the rhombomere 2 and Hox gene 3 specifically determines that of rhombomere 3 within the central nervous system, which of the statement(s) below are most likely true?

A) Hox gene 1 is likely expressed earlier than Hox gene 2, which in turn is likely expressed earlier than Hox gene 3 B) Hox gene 3 is likely expressed earlier than Hox gene 2, which in turn is likely expressed earlier than Hox gene 1 C) Hox gene 3 is likely expressed earlier than Hox gene 1, which in turn is likely expressed earlier than Hox gene 2 D) Hox gene 1 is likely expressed earlier than Hox gene 3, which in turn is likely expressed earlier than Hox gene 2

13. Which of the following statement(s) are most likely true? A) Transcription in mammals begins at the mid-blastula transition B) The fertilized egg in mammals gives rise to both embryonic and extra-embryonic tissues C) The extra-embryonic cells derived from the inner cell mass initiate the anteroposterior axis specification in the mammalian embryo D) Two of the above E) All of the above

14. Which of the following statement(s) are most likely true? A) The mammalian node is analogous to the Nieuwkoop center of the Xenopus embryo B) The Drosophila germband stage is analogous to the Xenopus gastrula C) All of the above D) None of the above

Exam 2

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22. BMP antagonists pattern: A) the anterior-posterior axis of the mammalian embryo B) the dorsal-ventral axis of the Xenopus embryo C) the left-right axis of the mammalian embryo D) Two of the above E) All of the above

23. The notochord: A) arises from the ectoderm B) arises from the endoderm C) secretes BMPs to pattern the neural tube D) secretes Sonic Hedgehog to pattern the neural tube

24. Which of the following could give rise to a two-tailed Drosophila embryo, as shown below?

A) a loss-of-function mutation in bicoid B) an embryo that expresses a functional Hunchback in both the anterior and posterior ends of the embryo C) a loss-of-function mutation in caudal D) Two of the above E) All of the above

25. Fibroblast growth factors (FGFs): A) are required in specifying the anteroposterior axis of the mammalian embryo B) binds G protein-coupled receptors C) are involved in Drosophila gastrulation D) Two of the above E) All of the above

26. A mouse embryo has loss-of-function mutations in retinoic acid-degrading enzymes. Which of the following would most likely occur? A) The mouse embryo would have defects in anterior structures B) The mouse embryo would have normal anterior structures C) The mouse embryo would have normal Hox gene expression D) None of the above

27. The embryonic epiblast gives rise to: A) mammalian extra-embryonic structures B) mammalian embryonic structures C) All of the above D) None of the above

Exam 2

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28. The mutant Drosophila has its antennae converted into legs. Which conclusion(s) would most likely be correct based on this information?

A) The fly could have a mutation in a gap segmentation gene B) The fly could have a mutation in a pair-rule segmentation gene C) All of the above D) None of the above

29. Which of the following statement(s) are most likely true? A) The Hox code hypothesis proposes that a certain combination of segment-polarity genes determines each segmental identity in vertebrates B) The Hox code hypothesis proposes that a certain combination of Hox genes determines each segmental identity in vertebrates C) The Hox code hypothesis proposes that all Hox genes within the vertebrate are completely redundant D) Two of the above E) All of the above

30. Which of the following statement(s) are most likely true? A) Paralogs are homologous genes with similar functions, which are present in different species that have descended from a common ancestor B) Paralogs always have the same functions C) Orthologs are homologous genes that resulted from gene duplication within the genome of an animal D) None of the above

31. The mammalian primitive streak is analogous to: A) the blastopore of the Xenopus embryo B) the Spemann-Mangold organizer in the Xenopus embryo C) the micropyle of the Drosophila embryo D) the germband of the Drosophila embryo

Answer Key

Testname: EXAM 2

1) A

2) B

3) D

4) D

5) C

6) B

7) E

8) B

9) B

10) C

11) C

12) A

13) B

14) D

15) C

16) A

17) A

18) E

19) B

20) D

21) C

22) E

23) D

24) A

25) D

26) A

27) B

28) C

29) B

30) D

31) A

32) B

33) E

34) A

35) D