GENETICS - Replication (UNIT 1)

13 flashcards · Other · by John Mark Webb

  1. EXTRACHROMOSOMAL DNA any DNA that is found off the chromosomes, either inside or outside the nucleus of a cell plasmid DNA mtDNA cpDNA

  2. Plasmid DNA in Bacteria extrachromosomal DNA is plasmid range in size from several thousand to 200,000 base pairs closed circular DNA Roles... defense against: antibiotics invaders (viruses) reproduction harmful environments specific products sexual reproduction Other roles... recombinant DNA genetic engineering Must have! origin of replication stripped down versions of "real" plasmid

  3. Characteristics of mtDNA 5-10 mtDNAs per mitochondria size: 16-18 kilobase human = 16,586 base pairs pure DNA, with the exception of the D-loop (D = displacement) closed circular (supercoiled) over 90% of mtDNA codes for RNAs - excepting 879 bp of heavy strand and 32 bp of light strand in D-loop are uncoding

  4. Why does mtDNA come from the mother (maternal)?

    the mitochondria in mammalian sperm are usually destroyed by the egg cell after fertilization

  5. The mitochondrial genome contains 37 genes that encode: 13 proteins (polypeptides) 22 tRNAs 2 rRNAs (12S, 16S)

  6. mtDNA semi-autonomous produces 40% of required proteins remainder from genomic DNA (nDNA) - all ribosomal proteins, membrane proteins, and Krebs Cycle enzymes, and remainder of ETS self-replicating and independently replicates replication similar to bacteria (rolling circle) genetic code (triplet) similar to that of bacteria has own ribosomes similar sized to bacteria (39S-28S) possesses unique DNA and RNA polymerases

  7. Chloroplast DNA (cpDNA) roles for photosynthesis (thylakoid structure, enzymes), transcription and translation and DNA replication 15-20 copies of DNA per cp range in cpDNA size 120-217 kb inverted repeats responsible for size variation 120 genes: 4 rRNAs 30-31 tRNAs 55 proteins 30 unknown proteins order of cp genes and their sequences highly conserved; some changes in gene order due to inversions

  8. cpDNA rate of mutation is 1/2 to 1/3 of nuclear 1/20th that of mtDNA codes for 1/3 of rRNA proteins (other 2/3 from nucleus)

  9. cpDNA mostly pure DNA w/in genes, some introns (16 genes) some repetitive DNA genetics highly variable between groups semi-autonomous produces most required proteins; remainder from genomic DNA self-replicating and independently replicates (replication similar to bacteria) genetic code (triplet) similar to that of bacteria has own ribosomes similar to bacteria (50S - 30S) inherited maternally in angiosperms inherited paternally in gymnosperms

  10. Endosymbiotic Theory mt from Proteobacteria - provide for aerobic respiration cp from Cyanobacteria - provide for photosynthesis semi-autonomous self-replicating and independently replicates similar genetic code similar ribosomes unique DNA and RNA polymerases

  11. Meselson & Stahl 1958 E. coli grown in 15N broth Heavy N (rare isotope) Ultracentrifugation Transfer to 14N broth

  12. Taylor, Woods, and Hughes 1957 Used tritiated thymidine (3H) which is found in DNA and no other molecule Grew cells for 1 cell cycle in the presence of tritiated thymidine and autoradiographed the cells Found that both chromatids of each chromosome were labeled Then grew cells for a second generation in medium that did not contain tritiated thymidine Found that only one chromatid of each chromosome was labeled These observations indicated that the DNA in the chromosomes replicated by semi-conse…

  13. Latt 1970 used a thymidine analog, which is just a similar molecule BrdU does not pick up a stain as well as thymidine