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UVM BCOR 103 - Final Exam Study Guide
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BCOR 103 1st EditionExam# 4 Study Guide Lectures: 21-27Lecture 21 (April09)- Componentso Nuclear Envelope Two lipid bilayers In between membranes is perinuclear spaceo NPC (Nuclear Pore Complex) Only way in and out of the nucleus, with the exception of hydrophobic steroid hormones (hydrophobic steroid hormones can diffuse across the membrane)o Nucleolus- ribosome productiono Light/Dark areas in transmission electron micrograph  heterochromatin/ euchromatin Light not condensed euchromatin, is expressed Dark  condensed  heterochromatin, no expressed- Chromatin- DNA and associated proteinso 30nm filamentso DNA alone is 2 nm- Nucleosomeso Key function: package DNAo 147 base pairs wrap around a nucleosome 1.75 times- Protamineso Help neutralize charge on DNA so it can be packagedo Spermatids don’t express genes, so genome can be condensed- Histoneso Amino/terminal tails  reversible translation modificationso Flexible o ~30 % of protein- ‘Histone Code’o Can be reado Written by writer proteins- Outer Membrane of nuclear envelope is contiguous with endoplasmic reticulum- Nuclear Laminao Meshwork of proteins and intermediate filaments that provides structural support for the nucleus- Prenylation: targets lamins to inner nuclear membraneo Prenyl group is 15 carbons long with a cysteine heado After Lamin A and Lamin C groups are inserted, the prenyl group are removedo Doesn’t happen with Lamin group B- Hutchinson-Gilford Progeria Syndromeo Lamins A and C mutations (dominant negative)deletionremoval of prenyl groups doesn’t occuro Nuclear morphological abnormalitieso Age 8-10X fastero Disorganization of heterochromatino Defective repair of DNA damage and increased genomic instabilityo Drug that helps: inhibitor of farnesyl transferase initially α-cancer drug- Transport into and out of the nuclear membrane by the NPCo ~30 proteinso Requires energyo Is selectiveo Receptor Proteins: In: importin Out: exportino RAS Family of small GTP binding proteins bound to- GDP: off- GTP: onLecture 22 (April 14) - Regulation of Nuclear Transporto Transcription factor import in response to cell signalingo NLS of NF-kB is masked by IkBo Phosphorylation of IkB targets for degradationo Import of NF-kB  Dephosphorylation of Pho4 unmasks an NLS- Selective import: may be regulated in response to cell signaling- Cell Signaling directs the import of transcription factor NF-kB through the action of a kinase that phosphorylates the NF-kB NLS is accessible to importin.- Nuclear import of the yeast transcription factor Pho4 is also regulated by phosphorylation. Cell signaling activates a phosphatase that dephosphorylates Pho4, thereby allowing importin to access its NLS. - Bottom Line: regulation of access of specific transcription factors to the nucleus acts to regulate the expression of the genes with which those transcription factors interact. - Androgen signaling: regulation of nuclear import in response to a steroid hormone.- Nucleolus: dynamic structureo Not membrane enclosedo Site of RNA Polymerase I (RNAPI) transcription of ribosomal RNA gene repeats.o RNAPI transcription is essential for nucleolus self-assembly.o Co-transcriptional assembly of rRNA with ribosomal proteins.o Metabolically active human cells: 5-10 million ribosomes/cell- Humans: ~200 rRNA gene tandem repeats on 5 chromosomes.- rRNA gene repeat: encodes three different rRNAs: 18S, 5.8S, and 28S.o The 4th rRNA (5S, rRNA) is not encoded within the tandem repeats, but rather from ~2,000 gene copies located within a single tandem array on human chromosome 1 (outside the nucleolus and transcribed by RNAPIII).- Synthesis of mature 18S, 5.8S, and 28S rRNA requires both endonucleolytic and exonucleolytic processing of a pre-rRNA. Cleavage of the primary transcript occurs co-transcriptionally. - 18S rRNA is incorporated into the 40S ribosomal subunit; 28S, 5.8S, and 5S are incorporated into the 60S ribosomal subunit.- Key Concept: nucleolus is a self-organizing structureo Self-organization is dependent upon rRNA transcription by RNAPI.o Blockage of rRNA transcription by DRB or actinomyosin D results in the disruptionof the structure of the nucleolus.- Key Concept: nucleolus is a highly dynamic structure whose activity is tightly coupled to the demand for protein synthesis. - Initial ribosomal subunit assembly occurs co-transcriptionally within the nucleolus.- Despite the amorphous appearance of the interphase nucleus in the electron microscope, the nucleus is highly organized. This organization is essential for function ofthe nucleus, especially gene expression. Nuclear organization is dynamic. - FISH: fluorescence in situ hybridization- Chromosome Territories: preferential positions of chromosomal DNA within the nucleus-dynamic, cell type specific.- Example: Hemoglobino Hemoglobin is a heterotetramer composed of alpha-globin (gene encoded on chromosome 6) and beta-globin (gene encoded on chromosome 11) proteins.o The alpha- and beta-globin genes become spatially juxtaposed within the nucleusof hematopoietic cells upon transcriptional activation.- Key Concept: dynamic changes in the positions of specific chromatin regions within the nucleus in response to cell development, differentiation or cell signaling.- Nuclear sub-components:o Not membrane boundo Self-organizingo Dynamic: responsive to cell signalingo Functional significance of many of these compartments has yet to be determined.- Open mitosis: dissolution of the nuclear envelope and consequent mixing of nuclear andcytoplasmic components- Key concept: sorting of nuclear and cytoplasmic components following cytokinesis is accomplished by nuclear import into the reassembling nucleus. Lecture 23 (April 16)- Key concept: complexity of an organism does not correlate directly with genome size or the total number of genes in the genome.- Genomics: the systematic analysis of entire cell genomes- First human genome sequence (2000): ~10 years of work, cost $2.7 billiion- Key concept: Organism complexity does correlate with the percentage of the genome that encodes protein (inverse correlation).o Example: human dystrophin gene (encodes a protein that is part of the complex that connects the cytoskeleton to the extracellular matrix)dystrophin gene: 2.5 million bases, 79 exons, final mRNA is 14,000 bases (0.61% of the pre-mRNA)- Alternative Splicing: Production of Multiple Proteins from single geneo Alternative splicing >90% of human genes-


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UVM BCOR 103 - Final Exam Study Guide

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