19 Eukaryotic Genomes
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Created by:
ttrimble11 on January 29, 2011
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45 terms
Terms | Definitions |
|---|---|
 chromatin | highly structural DNA protein complex |
| histones | proteins responsible for the first level of DNA packing in chromatin |
| nucleosome | "bead" basic unit of DNA packing |
| linker DNA | string between beads that joins together |
| heterchromatin | highly dense chromatin during interphase -not transcribed |
| euchromatin | less condensed chromatin which makes its DNA accessible to enzymes & transcription |
| cell differentiation | during development cells undergo a process of specialization in form & function |
| differential gene expression | expression of different genes by cells with same genome-regulated at transcription |
| histone acetylation | acetyl groups are attached to positively charged lysine in histone tails-positive charge neutralized & no longer bind to neighboring nucleosomes-promotes folding of more compact chromosome |
| methylation | addition of methyl groups leads to condensation of chromatin |
| histone code hypothesis | specific combination of modifications determines chromatin configuration |
| genomic imprinting | methylation permanently regulates expression of either maternal or parental allele of certain genes at development |
| epigenetic inheritance | inheritance of traits transmitted by mechanisms not directly involved in nucleotide sequence |
| control elements | segments of noncoding DNA that help regulate transcription by binding to different proteins |
| transcription factors | required by eukaryotic RNA polymerase to initiate transcription |
| enhancers | distal control elements-may be thousands of nucleotides upstream or downstream from gene |
| activator | protein that binds to an enhancer & stimulates transcription |
| proximal control elements | control elements located close to promoter |
| mediator proteins | protein mediated bending of DNA brings in bound activators |
| repressors | transcription factors function to inhibit expression of a particular gene |
| silencing | recruiting proteins that deacetylate histones-leading to reduced transcription |
| combination of control elements | more important than the presence of a single unique control element |
| alternative RNA splicing | ex. of regulation at RNA processing level-different mRNA molecules produced by same transcript-depends on which RNA segments are treated as exons or introns |
| microRNA | single stranded RNA molecules that bind to complementary sequences in mRNA molecule-degrades target mRNA or blocks its translation |
| RNA interference | inhibition of gene expression by RNA molecules |
| siRNA | small interfering RNA |
| ubiquitin | small molecules that mark a particular protein for destruction |
| proteasomes | giant protein complexes that recognize ubiquitin-tagged protein molecules & degrade them |
| oncogenes | cancer causing genes in certain retroviruses |
| tumor virus | cause cancer in various animals-transform cells into cancer cells through integration of viral nucleic acid into host DNA |
| proto-oncogenes | normal cellular genes that code for proteins that stimulate normal cell growth & division |
| tumor suppressor gene | proteins encoded help prevent uncontrollable cell growth |
| ras gene | G protein that relays a signal from a growth factor receptor on plasma membrane to a cascade of protein kinases-mutations results in increased cell division without a growth factor |
| p53 gene | codes for specific transcription factors that promote the synthesis of cell-cycling-inhibiting proteins |
| repetitive DNA | most intergenetic DNA-present in multiple copies of the genome-made up of transposable elements |
| Barbara McClintock | breeding experiments with maize led to discovery of transposons |
| transposons | move within a genome by means of a DNA intermediate either cut & paste or copy & paster |
| retrotransposons | move by means of RNA intermediate-always leave copy at original site during transposation |
| Alu elements | transposable element related DNA of similar sequences that do not code for any protein-transcribed into RNA molecules |
| simple sequence DNA | contains many copies of tandemly repeating short sequence |
| satellite DNA | repetitive DNA isolated in a band in a centrifuge tube |
| multigene families | collections of identical or very similar genes |
| pseudogenes | nonfunctional nucleotide sequences quite similar to functional genes |
| nonidentical genes | two related families of genes that encode globins |
| exon shuffling | mixing & matching of different exons either within a gene or between two nonallelic genes owing to errors meiotic recombination |
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