Ch 15 -.Gene Regulation  Prokaryote Regulation Operon * not found in eukaryotes Operon * not found in eukaryotes Regulator gene = codes for repressor. Active repressor binds to operon Regulator gene = codes for repressor. Active repressor binds to operon Promoter – where RNA polymerase attaches Promoter – where RNA polymerase attaches

2 types of regulators  Repressible operon 1 – always “on” = repressor cannot bind, therefore RNA polymerase can attach and protein is made. 1 – always “on” = repressor cannot bind, therefore RNA polymerase can attach and protein is made. Ex. Trp operonEx. Trp operon -To turn off the protein product binds to repressor = repressor can bind & transcription ceases

Inducible Operon  2 – always “off” = repressor can always bind therefore RNA polymerase cannot attach = no protein produced Ex. Lac operon Ex. Lac operon

Presence of molecule (inducer) turns on transcription by binding to lac repressor to disable binding.

Eukaryotic Regulation  – allows differential protein expression dependent on specialized function of cell.  5 ways [3** within the nucleus & 2## in the cytoplasm]

 1** – chromatin structure – packaging makes RNA [epigenetic] polymerase binding impossible * cancer results when mutations occur in transcriptional factor genes.

2** – Transcriptional control – [transcription factors- proteins that initiate RNA pol. binding] once a gene is unpackaged it will be transcribed. (transposons shut down genes by interrupting code, gene jumping, also encourages mutations)

3** – posttranscriptional control-mRNA processing excising introns

4## - translational control – poly a tail protects mRNA from being degraded & allows for translation

5## - Posttranslational control – modification of a protein after synthesis determines biological activity.

Chromatin Structure  DNA wrapped around 8 histones  DNA = histone = nucleosomes  Highly condensed = heterochromatin – inactive, methyl groups  Loosely condensed = euchromatin – active * have attached acetyl group. DNA can be methylated = not expressed can be inherited that way

KINASES  Proteins that dephosphorylate to signal protein expressions in membrane to nucleus regulatory pathway

TRANSPOSONS  Jumping genes of repetitive sequence that interrupt gene expression

GENETIC MUTATIONS- good, bad, non effective 1-germline → passed on 2- somatic → not passed on → cancer

MUTATIONS [causes- spontaneous, environ. mutagens, inherited0 Point Mutations- Change a single base → change codon Point Mutations- Change a single base → change codon Frame shift mutations- deletion or addition result in a completely new amino acid sequence. Frame shift mutations- deletion or addition result in a completely new amino acid sequence. Mutations in proto-oncogenes or tumor suppressor → cancer Mutations in proto-oncogenes or tumor suppressor → cancer

Study Questions  What part of mRNA sections are spliced together into the finished mRNA molecules?  What are 4 potential control mechanisms for regulation of gene expression in eukaryotic organisms?  What is the correct order of protein synthesis?

Study Questions  What is the role of DNA in controlling cellular activity?  What word describes the attachment of groups of particular amino acids of specific proteins to nucleosomes as thought to be an important control mechanism for gene expression?  Define the term gene

Study Questions  The expression of genes can be controlled at what 4 stages of protein synthesis?