ICQs21,22.ppt

Which one of the following classes of Drosophila genes does not play any role in the process of segmentation along the A-P axis? egg polarity genes gap genes pair-rule genes segment polarity genes Hox genes 2. What establishes the anterior boundary of each Hox gene? gap gene combinations pair rule gene combinations A and B segment polarity genes the boundary of expression of other Hox genes Possible Class 21 ICQs 3. What establishes the posterior boundary of each Hox gene? gap gene combinations pair rule gene combinations A and B segment polarity genes the boundary of expression of other Hox genes 4. Loss of function mutations in a Hox gene generally result in homoeotic defects (normal structures formed in abnormal places) that can be described as: a. posterior-to-anterior transformations b. anterior-to-posterior transformations 5. Hox genes encode: a. Paracrine ligands b. Juxtacrine ligands c. Endocrine ligands d. Transcription factors e. Receptors 6. What would the phenotype of a fly be if the whole Bithorax complex was deleted? a. T1 T2 T2 A1 A2 A3 A4 A5 A6 A7 A8 b. T1 T2 T3 A1 A1 A1 A1 A1 A1 A1 A1 c. T1 T2 T3 A1 A2 A3 A4 A4 A4 A4 A4 d. T1 T2 T2 T2 T2 T2 T2 T2 T2 T2 T2 7. When two genes are paralogous, what does that mean? They are dervied from the same ancestor They have the same function as a common ancestor They are duplicated from the same ancestor They are orthologous 8. How does the node move during chick and mammalian gastrulation? a) Starts at the anterior, moves first posteriorly and then retracts toward the anterior. b) Starts at the posterior, moves first anteriorly and then retracts toward the posterior. c) Starts at the anterior with the primitive streak; ends up at the posterior after primitive streak elongates. d) Starts at the posterior with the primitive streak; ends up at the anterior after primitive streak elongates. 9. Hoxc-8 in mouse is expressed in cells that give rise to the first lumbar vertebra. If you generated a knockout mouse for this gene, what might you expect to find? The first lumbar vertebra would look like the second. The last thoracic vertebra would look like the first lumbar The first lumbar vertebra would look like the last thoracic vertebra. The lumbar vertebrae would be missing 1. How would the derivatives of the somite be affected by removal of the overlying epidermis? Scleratome would not develop properly Myotome and dermatome would not develop properly No derivatives would form normally All derivatives would form normally Possible Class 22 ICQs 2. Using homologous recombination, scientists generated a transgenic mouse in which the MyoD coding sequence was replaced with Myf5 coding sequence, still under the control of the MyoD promoter. The mouse was normal. What does this suggest? MyoD and Myf 5 are redundant MyoD and Myf 5 have different functions MyoD and Myf 5 cannot substitute for each other’s functions 3. Take a minute to think about this with your group and write down your answer and explanation In the human syndrome Campomelic Dysplasia, individuals have malformed ribs and trachea, overall shortened skeletal bones, and usualy die from respiratory failure Can you think of a single mutation that could account for these phenotypes? Sox-9 is probably the best candidate. Interestingly,XY individuals with this mutation look female because Sox-9 is also involved in primary sex determination. 4. Which of the following structures is mesenchymal in an adult organism? a. Cartilage b. Bone c. Muscle d. Dermis e. all of the above 5. Think about this with your group What might be the cause of osteoporosis? Write down your answer 6. Consider this: Chick and mice have some pretty obvious differences. One of these is that mice have teeth and chick do not. However: Undifferentiated chick jaw epidermis was combined with undifferentiated mesenchymal cells from the mouth area of mouse in culture. When the epidermis differentiated, it made tooth-like structures, “hen’s teeth”. The converse experiment, chick mouth mesenchyme with mouse epidermis did NOT yield teeth. What can you conclude from this experiment? The chick epidermis does not normally make teeth because it is not competent to do so. The chick epidermis does not normally make teeth because the underlying chick mesenchyme does not send “tooth” signals The mouse and chick mesenchyme send the same signals; the epidermis just responds differently.