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7 Cards in this Set
- Front
- Back
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Prokaryotes vs. eukaryotes
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Pro:
-small(10^5-10^6bp) -genes and prots are co-linear=gene is simple triplet code for prot -one chrom and one copy of that chrom -circular Eu: -large(10^7-10^9) -large expanses of junk DNA interupt (introns) gene, <5% of human genome codes prots -sexual reproduction-haploids to diploids -mult linear chroms(yeast=16,humans=24) -primary genome in nucleus(except mito and chloroplasts) |
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cell replication needs
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need:
1)centromere-mediate sgregation during cell division 2)telomere to guard against erosion of chromosome ends 3)Origin(s) of replication |
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Centromere
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-In S-phase (replication) copy each chromosome(maternal and patern.) to make two pairs of identical sister chromatids(mat and pat)
-sister chromatids are linked by centromere(typical 1000's of bp, one cent/chromosome, not always in middle) -when mitosis happens kinetochores attach to centromeres to reg:alignment in middle, splitting, draging to poles of chromes -mistake in segregation=aneuploid(wrong # of chromes), cause cancer |
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Telomere
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-protect ends of chromosomes
-made by telomerase at end w/o template to replace lost telomeres from lagging strand synth. -form T-loops by looping back and bonding with itself to protect ends from degredation or repair -aging-run out of telomeres=can't keep dividing -cancer can force dividing-crisis point-killed or re-express telomerase |
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nucleosome
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-nucleosome=DNA wrapped around octamer-two of each of four histones
-Histones-globular with tail positive charge interact w/ neg charge of phosphate backbone 30nM solenoid-nucleosomes held together by H1's |
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Euchromatin vs. heterochromatin
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Eu:
-loosely packed -highly transcribed Heter: -tightly packed -All DNA before mitosis -silent genes, repetitive DNA (e.g. centromeres) |
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chromatin remodeling
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-regulation of chromatin state by adjusting nucleosome positioning
-requires multi-protein complex and E from ATP -by covalent modification of histones-histone modifying enzymes (ex. neutralize pos charge on hist.) -phosphorylation-important for chromosome condensation prior to cell division |
