Chapter 11 Gene Expression Over Time Changes in gene expression may occur over time This may occur at the molecular tissue or organ gland level May be a response to environment Gene expression differs in different cells Example Globin Chain Switching changes in hemoglobin Adult hemoglobin has four polypeptide chains Genes for alpha and beta subunits are located on chromosome 11 and 16 respectively Subunits change in response to oxygen levels Subunit makeup varies between embryo fetus and adult Hemoglobin Heme group is O2 bound Embryonic epsilon and zeta chain Fetal gamma and alpha chain Adult beta and alpha chain The Proteome Proteins 14 types Control of DNA Expression altering manufacture of mRNA by chromatin remodeling Chromatin dna proteins Transcription Factors necessary for transcription to occur RNA polymerase also needed for transcription 1 Promoters mutate alter how it interacts with transcription factors and RNA polymerase 2 Multiple 2 copies of gene Control of Expression 1 Chromatin remodeling 2 RNA interference Enhanceosome attach to DNA and attract other proteins acetylase Acetylase adds acetyl groups to tails acetylation 8 histones DNA nucleosome All DNA histones chromatid TATA is the promoter DNA Methlation Parent genes turn on and off Example of epigenetic changes deals with access to the molecule Methylated DNA binds all histones together and makes DNA inaccessible Genetic imprinting Acetylated DNA more accessible DNA is able to be transcribed Control of DNA Expression RNA Interference happens after transcription mRNA dismantling prevent mRNA from doing its job Single strand shown below can be matched up to itself Known as a hairpin loop sometimes gives you double stranded RNA Double stranded RNA bad Dicer Cuts RNA siRNA short interfereing RNA strands double strands separate siRNA associates with RISC RNA induced silencing complex slicer RISC finds target mRNA and marks it for death mRNA prevented from completing its task Proteins Outnumber Genes 1 5 of human genome encodes protein 25 000 genes specify up to 200 000 proteins Alternative splicing and cutting proteins translated from a single gene Introns may function as exons Larger proteins may be edited into 1 smaller proteins Alternate Splicing exon contributes to protein blocks of information introns may be used DPP and DSP Dentinsialophosphoprotein dentin DPP DSP collagen dentin Majority of Human Genome Does Not Encode Protein Rest of genome encodes for Viral DNA 8 borrowed retroviruses RNA get turned into DNA and makes virus parts Noncoding RNAs transcribed not translated major regulation Other controls enhancers Introns Promoters Repeats transposons jumping genes telomeres ends of chromosomes centromeres attachment points pseudogenes others Disease Dentinogenesis imperfecta decrease in DPP usually dentin wears down more quickly