BIO 1A03 Midterm 2 Questions and Answers Graded A

BIO 1A03 Midterm 2 Questions and Answers Graded A Prokaryotic growth and cell division -nutrient-rich environment -favorable temperatures Housekeeping genes -genes required at all times for normal function -all ways transcribed and translated -allow constant maintance for general cellular activity -e.g. structural protein of a cell, DNA and RNA polymerase, genes coding for ribosomal proteins -constitutive Regulated genes genes that can be turned on and off at a needed basis Francois Jacob and Jacques Monod -discovered that lactose in the growth medium induced expression of the B-galactosidase gene Reason Lac system is utilized -methods were developed to easily visualize and manipulate lacZ expression, the promoter, operator (lacO), repressor (lacI) Uses for Lac System -in clonning DNA fragments, genes -reporting gene expression -visualizing in situ (in vivo) gene expression -protein localization -two hybrid screens -segregation of replicating chromosomes (lacO) -mutagenesis -genetic analysis pUC1 and pUC19 family of cloning vectors -used for cloning DNA fragments into the "plink" site, disrupting lacZ gene Lactose Operon being negatively regulated -the transcription and translation of lacI prevents transcription of lacO Presence of lactose -binds to the LacI inhibiting it from binding to lacO. Thus, transcription of LacO will continue Ortho-nitrophenyl-B-galactoside (ONPG) - an analogue of lactose -when ONPG is hydrolyzed, galactose and ortho-nitriphenol are released -ortho-nitriphenol absorbs 420 nm of light and appears yellow Important analogues of lactose -B-D-galactophranosyl- (1-4) D glucose -isopropyl B-D-1-thiogalactophranside (IPTG) (induces lac operon, is not metabolized) Allosteric effector IPTG binds to the LacI receptor Gene expression -the functional product of the gene is made, modified and activated -transcription, translation and protein modification is completed Transcriptional control allows for the transcription of DNA to mRNA Translational control allow for the translation of mRNA to proteins Post-translational regulation -allows cells to have a stockpile of protein in the cell that is simply inactive -once the cell recieves a signal, this can lead to simple modification to turn on all the inactive proteins -fast and can result in quick cellular responses to changes that are brought about in the environment Post-translational control -allow for modifications and activation of produced proteins -fastest control mechanism Transcriptional regulation -controls amount of mRNA being produced in the cell -activation of transcription requires that proteins bind to the promoter and increase the binding of RNA polymerase -this can activate or inhibit transcription -slowest mechanism -happens with more drastic environmental changes that the cell is exposed to Slowest level of regulation but most efficient -transcription -the cell does not waste energy or resources making mRNA or polypeptide unless it is needed -e.g. increase gene expression of B-galactosidase gene during the presence of lactose Fastest level of regulation post-translational modification Initiation of translation in prokaryotes the ribosome binds to the specific Shine-Dalgarno sequences Initiation of translation in eurkaryotes the binding of ribosome to the 5' end or 5' CAP of mRNA Amount of protein produced -depends on the rate of translat