BSC 114 Exam 4 Questions with Correct Answers Latest Update

BSC 114 Exam 4 Questions with Correct Answers Latest Update Gene Expression - Answers gene → mRNA → protein; steps where it is regulated include transcription (most important), splicing (only in euks), translation, mRNA stability, protein stability Differential Gene Expression - Answers ea. cell expresses only a subset of its genes (humans ~20%); due to specific combo of activator proteins Gene Regulation - Answers mechanism of differential gene expression Regulation of Bacterial Transcription: TRP Operon - Answers 3 trp enzymes are the products of the 5 genes (2 of which are dimer proteins); 5 genes are adjacent & transcribed as single long mRNA Regulation of Bacterial Transcription: TRP Operon Repression - Answers when tryptophan available trp operon repressed (turned off; no need to make tryptophan) but turned on when tryptophan is absent; protein repressor produced by trpR gene binds to operator, a DNA seq. @ beginning of operon, blocking trxn; reg. proteins bind to a seq. in DNA molecule near promoter Negative Regulation - Answers binding of the regulatory protein prevents trxn; ex: trp repressor regulation of trp operon Positive Regulation - Answers binding of re. protein is necessary for transcription Transcriptional Regulation in Euks - Answers DNA-binding proteins (trxn factors) bind to control elements (DNA seq.) & activate transcription (+) or repress (-); trxn. factor proteins bind to control elements to promote trxn. General Transcription Factors & Mediators - Answers bind to proximal control elements & the promotor Activators - Answers bind to enhancers Combinatorial Control - Answers cell specific transcript. results from diff. combos of trxn factors; differential presence of trxn factors is due to earlier differential gene express; diff. cell types come about through seq. of differential express. of trxn factors; last "generation" of trxn factors turns on genes that encode specialized proteins Chromatin Structure - Answers regulated by chem. modifying histones & DNA Histone Acetylation - Answers addition of acetyl groups (acid0 promotes a "looser" chromatin structure and promotes gene expression DNA Methylation - Answers methyl groups added to base C to repress trxn through altering chromatin structure Epigenetic Inheritance - Answers modifications & patterns of gene expression are passed down @ cell division to descendent cells Promoter - Answers proximal/close to gene being expressed control elements Enhancer - Answers distal/far from gene being expressed control elements; proteins bound to this make contact w/ & stimulate RNA polymerase via looping of intervening DNA Alternative Splicing - Answers primary transcript may be spliced in diff. ways Small RNAs may regulate mRNA stability & translation - Answers miRNA: micro RNAs that do not code for protein seq. but bind to target mRNA to induce mRNA degradation or translation inhibition siRNA: short interfering RNAs that do not code for protein seq. Both are 20-23 nt RNA molecules Differentiation - Answers cellular specialization; cell acquires its final specialized form Determination - Answers cells acquire info & become committed to a particular fate in the organism; under genetic control; precedes differentiation Pattern Formation - Answers spatial control of gene expression, determination & differentiation; diff. patterns arise b/c regulatory molecules are distributed asymmetrically Asymmetric Regulatory Molecules - Answers ~unequal cytokinesis & diff. cytoplasmic contents (molecules = cytoplasmic determinants) ~different extracellular signals (process = induction) Homeotic Genes - Answers "master genes" that control cellular identity; regulate the anterior-posterior development of all bilateral animals; these proteins are trxn factors Cancer - Answers disease of unregulated cell proliferation; loss of inhibition of proliferation; loss of cell adhesion (ability to leave tumor & move elsewhere); ability to stimulate vascularization Cancer & Genetic Control - Answers Cell proliferation is genetically controlled signaling processes... neighboring cells may stimulate or inhibit cell division And regulations of trxn... entry into mitosis involves adoption of an internal genetic program Proto-oncogenes - Answers encode proteins that promote cell division Tumor-suppressor Genes - Answers encode proteins that repress cell division Oncogenes - Answers mutant version of proto-oncogenes; mutant proteins promote cell division, but lack the ability to be regulated; only takes one mutant allele to promote cancer in a dom. manner Mutant Tumor-suppressor Genes - Answers encode defective proteins that do not repress cell division; recessive, both genes must be mutant for cancer progression Positive Regulators of Proliferation & Cancer - Answers mutations can cause protein to get stuck in the "on" position; resulting in inappropriate cell proliferation; ex:) oncogene Negative Regulators or Proliferation & Cancer - Answers mutation alleles produce a non-functional protein that fails to act; ex:) tumor-suppressor genes