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midterm_2_06_key - Bio 120 Midterm 2 KEY Name Bio 120...

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Bio 120 Midterm 2 2/21/06 KEY Name : ______________________________ 1 Bio 120 Development Midterm 2 2/21/06 KEY Question 1 DEFINE THE FOLLOWING 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 . 10 points each. Maternal-effect mutation Mutation in which phenotype of zygote is determined by its mother’s genotype. Niche Specific region of an organ where stem cells reside. X-inactivation In XX mammals, process in which gene expression from one copy (usually random) of X is reduced, allowing dosage compensation. Involves noncoding RNA and DNA methylation. Maintenance Methyltransferase Eznyme that restores complementary methyl to an unmethylated cytosine of a CpG. (In mammals, plants) Polycomb group gene Genes that, like Polycomb, are required for stable repression of homeotic (or other) genes; encode components of chromatin Blastocyst Stage of mammalian embryogenesis equivalent to blastula, composed of inner cell mass and trophectoderm surrounding a blastocoel; stage at which embryo implants into uterine wall. LSDS mechanism Localized source-dispersed sink mechanism, model for generation of exponential decay gradient of a substance/morphogen. MyoD Transcription factor involved in muscle development. Sufficient to convert fibroblasts to myoblasts in culture. Not required for muscle development in vivo due to redundancy with Myf5. Stem cell Any cell that is both self renewing and also gives rise to more differentiated cells. Found in adult tissues. Embryonic stem cells are derived from the inner cell mass.
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Bio 120 Midterm 2 2/21/06 KEY Name : ______________________________ 2 Pluripotency Ability of a cell to generate multiple but not all different cell types.
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