BCHM 3050 1st Edition Lecture 18 Outline of Last Lecture I. How Sanger Sequencing WorksII. Southern BlottingOutline of Current Lecture I. Triple Stranded DNAII. Prokaryotes vs. EukaryotesIII. TransposonsIV. Comparing Genome Segments from Selected OrganismsV. General Characteristics of DNA ReplicationVI. Meselson and StahlVII. Replication OriginsVIII. Summary of DNA ReplicationCurrent LectureI. Triple Stranded DNAa. Triple helix – facilitates role to enable crossing over/recombination in meiosisb. Polypyrimidine breaks off and forms additional bonds with other bases to form triple helix àunstable formII. Prokaryotes vs. Eukaryotesa. Eukaryotes have a lot of interruptions in its DNA, discontinuous à 95% of our DNA does not code for anythingThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. Do not have operons, everything has their own control unitc. Operons – one control unit and everything in controlled by that unit; found in prokaryotesIII. Transposonsa. Transposons = “jumping genes”b. Transposons cause random mutation – some parts of DNA moves from one chromosome to anotherIV. Comparing Genome Segments from Selected Organismsa. Notice the amounts of non-coding DNA in Humans & Corn vs. yeast & E. coli.b. Also, notice the amounts of introns and especially the small amounts of coding specifically for genes in Human DNA.c. Finally, Humans also have large amounts of DNA coding for tRNA’s.d. Pseudogenes are only found in high organisms like humans (not in prokaryotes)e. Empty spaces = genes that code for tRNAV. General Characteristics of DNA Replication a. Chemically uni-directional (5’ à 3’)b. Semi-conservativec. Spatially bi-directional – DNA goes in both direction from a single pointd. Semi-discontinuouse. Adding new nucleotides to a growing chain of DNA is essentially DNA replicationf. Red = leading strand, made continuouslyg. Green = lagging strand, made discontinuously; made in piecesh. DNA replication is considered semi-discontinuousi. Okazaki = scientist who discovered lagging strands à “okazaki strand”j. “Lagging” does not refer to a lag in time or that the replication is slower in that standVI. Meselson and Stahla. Meselson and Stahl proved that DNA is semi-conservative!b. Conserve 50% and make the other 50% from scratchc. -DNA replication happens in the nucleus of the cell at first – DNA strands are separatedd. DNA can be labeled by its phosphorus, nitrogen, oxygen, or carbone. Labeled nitrogen in the DNA of bacteria by labeling nitrogen in the food that theygave the bacteriaf. Labeled both strands of DNA with the heavy form of nitrogen, N15g. Bacteria divide every 20 minutes à the new DNA that was made had N14 instead of N15 for one strand à DNA is semi-conservativeh. Conservative is unequal sharing of DNA à mother cell gives all DNA to one daughter cell and makes other daughter cell get DNA from scratchVII. Replication Originsa. Origins of replication are defined by certain sequencesb. All prokaryotes have the same origin; most eukaryotes have the same originsc. Break DNA open at the origin, replication occurs in 2 directions à both 5’ to 3’d. Eukaryotes have many origins sequences scattered throughout à DNA breaks at different origine. Replication bubbles – when DNA breaks at originf. All strands are leading strands in this picture (red)VIII. Summary of DNA Replicationa. As leading strand is being made, the zipper of DNA opens up more and moreb. Enzyme that carries out DNA replication is DNA polymerasec. Polymerase needs a primer (existing stretch of nucleotide) d. RNA primers e. Memorize the functions of all of the proteins involved in DNA replication:f. Helicase – opens the DNA from the origins of replicationg. DNA polymerase (III) – enzyme that added nucleotidesh. RNA primase (primers)i. DNA ligases – joins the Okazaki fragmentsj. DNA polymerase
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