midterm_2_04_key

midterm_2_04_key - Bio 120 Midterm 2 May 13th 2004 Name:_...

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Bio 120 Midterm 2 May 13 th 2004 Name: ______________________________ 1 Bio 120 Development Midterm 2 May 13 th 2004 KEY Question 1 DEFINE ANY EIGHT OF THE FOLLOWING TEN TERMS, as used in developmental biology, in the space provided, using diagrams as necessary; if the term applies to a particular species or animal group, say which . 5 points each. Zygotic mutation Mutation in which phenotype of zygote is determine by its own genotype (as opposed to maternal-effect mutation) Follicle cell In Drosophila/insects, somatic cell in epithelial layer that surrounds germline cells of cyst X-inactivation In XX mammals, process in which gene expression from one copy (usu. random) of X is reduced, allowing dosage compensation. [involves Xist RNA and methylation.] Primordial germ cell Generic term for embryonic precursor of germline cells. Polycomb group Genes that, like Polycomb, are required for stable repression of homeotic genes; encode components of chromatin Nieuwkoop center Dorsal organizing center of early (2-32 cell stage) amphibian blastula; located in dorsal vegetal cells. LSDS mechanism Localized source-dispersed sink mechanism, model for generation of exponential decay gradient of a substance/morphogen. Nuclear transfer
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Bio 120 Midterm 2 May 13 th 2004 Name: ______________________________ 2 Used in animal cloning; transfer of nucleus from donor cell into enucleated oocyte, yielding nucleus in foreign cytoplasmic environment. French Flag Model Model of pattern formation in which morphogen gradient specifies different cell fates in field of cells. Pluripotency Ability of a cell to generate multiple but not all different cell types. Question 2 In each group of statements, either three are false and one is true, or one is false and three are true. Indicate which is the ‘odd man out’ and whether it is true or false . 10 points each. (a) Germ line development in Drosophila Pole plasm contains ribonucleoprotein particles. Pole cells migrate from the posterior pole to the future gonad. Oskar is sufficient to organize pole plasm. A zygote that lacks pole plasm should be fertile. false (b) Drosophila oogenesis Toll is expressed by follicle cells. Oocyte microtubules have their minus ends at the future posterior. A cyst consists of 16 cells connected by cytoplasmic bridges. true The dorsal pole is specified by the point of sperm entry. (c) Drosophila segmentation Pair rule gene expression is activated by the segment polarity genes. The even skipped stripe 2 enhancer contains binding sites for nanos. The extended germ band is divided into parasegments. true Mutations in gap genes affect alternating parasegments. (d) Drosophila homeotic genes Loss of function in Antennapedia causes an antenna-to-leg transformation.
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midterm_2_04_key - Bio 120 Midterm 2 May 13th 2004 Name:_...

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