Organization and control of Eukaryotic chromosomes More complex than prokaryotes Associated with proteins that help pack DNA DNA of prokaryotes makes proteins, tRNA, mRNA, or are control elements Much of eukaryotic DNA is noncoding and function unknown

Eukaryotic control Epigenetics Packing by deacetylation (acetylation loosens chromatin packing) of histone and methylation of DNA RNA polymerase may not be able to access the DNA

Barr bodies Imprinted genes Some genes are silenced (by methylation) depending on if you inherited from mom or dad Example: Ligers Prader-Willi Syndrome- mothers genes for 7 genes on chromosome 15 are imprinted (methylated) -deletion in this region on dad’s chromosome Angelman Syndrome-ONE gene is paternally imprinted -maternal deletion results in one “missing” gene https://www.youtube.com/watch?v=1zOWYj59BXI

Transcriptional control of gene expression Enhancers Segments of DNA far away from gene that bind activators Activators in turn help to bind transcription factors and initiate transcription

Post transcriptional control -RNA processing Alternative splicing -mRNA degradation RBC have globin mRNA that are very long lived RNAi  RNA interference -microRNA’s bind to complementary RNA, blocking -Translational control Some proteins attach to the leader region of mRNA and prevent the ribosomes from attaching

Post transcriptional control Protein modification Cutting polypeptide into segments Adding prosthetic groups (heme group in hemoglobin) Transport to cellular location Selective protein degradation Tagged with ubiquitin Disposed of by a protease