BIO314 Full Practice Exam 2

BIO314 Full Practice Exam 2 - BIO 314 Practice Exam#2 1 Of...

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BIO 314 Practice Exam #2 1) Of the following, which is an incorrect statement? a) Cancer promotes growth (anti-apoptosis/pro-survival) by both modifying existing signaling pathways/cascades , that is to say deregulate and modify existing cellular circuitry, and erecting novel pathways. b) A signaling pathway/cascade is initiated when a ligand (a chemical messenger) binds to a receptor on the extracellular face of the plasma membrane. The effects of the cascade therefore start at the plasma membrane and can travel as far as the nucleus. c) Mitogens, growth factors (GFs), provide a means for mitosis as cells are metabolically active; when mitogens are depleted or when cells are serum starved cells do not die, they simply stop dividing (withdrawal from the cell cycle). d) Immediate early genes (IEGs) are genes whose expression was upregulated after the introduction of mitogens. Some IEGs are transcription factors that are capable of inducing a secondary wave of gene expression (activation of delayed early genes) and whose gene products may lie in various compartments of the cell (nucleus, cytoplasm, etc.). e) All of the above are incorrect statements. 2) Of the following, which is an incorrect statement? a) Son of Sevenless (SoS) is a guanine nucleotide exchange factor (GEF) that takes proteins from a GDP bound (inactive state) to a GTP bound (active state); Sos is also a homolog of epidermal growth factor receptor (EGFR) and is part of a larger signaling cascade that leads to the activation of Ras. b) When comparing the Src Homology (SH) domains we see that it is a highly conserved process in terms of sequence regions, shape and function within the same and different species. c) There are three (03) SH domains: SH1, SH2 and SH3. SH1 is the catalytic domain and is the binding site for ATP; SH2 and SH3 act as the enzyme regulator and substrate recognition regions. d) When a ligand binds to a receptor and causes autophosphorylation in trans tyrosines are phosphorylated (Y à pY); the SH2 domain of a protein binds to the cytoplasmic pY and the neighboring three to four amino acids (the oligiopeptide region) – the unit as a whole is the “docking site” – it is in this position that this SH2 containing protein can act as a “bridge” or “adaptor” molecule (i.e. Shc OR Grb2). e ) All of the above statements are true. 3) The Ras effecter pathway… a) …is dependent on the activation of Ras from a GDP bound state (inactive state) to a GTP bound state (active state) from its (inactive Ras’s) interaction with a guanine neucleotide exchange factor (GEF), i.e. the proximity of Son of Sevenless (SoS). b) …can activate Raf (MAPKKK) and initiate a kinase cascade that sees the phosphorylation of serines (S) and tyrosines (Y), which leads the activation of early genes.
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This note was uploaded on 01/04/2011 for the course BIO 314 taught by Professor Erster,s during the Spring '08 term at SUNY Stony Brook.

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BIO314 Full Practice Exam 2 - BIO 314 Practice Exam#2 1 Of...

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