BIOLOGY 207 Lecture 6 Outline of Previous Lecture I. Cell Wall and MembraneII. Cell TransportationOutline of Current Lecture I. DNA ReplicationII. TranscriptionIII. TranslationCurrent LectureInformation Flow“Central Dogma”I. DNA Replicationa. Semi-Conservative Processi. Replication of one strand of parent DNA results in two identical daughter strandsii. The parent is used as a template to create these two daughters, as complementary nucleotides are added to the strand of DNAThese 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. DNARNAProteinTranslationDNA ReplicationTranscriptionb. Origins of replicationi. DNA can start replicating once the two strands separate to be copiedii. The “replication fork” is what appears upon being unwound by the enzyme, DNA helicase, forming a Y from the two strandsiii. Of the two strands, there is a leading and a lagging, each of which replicate in opposite directions to opposite strand ends 1. Single stranded binding proteins (SSB) work with the helicase to keep the strands from winding back togetheriv. The leading strand is replicated with the nucleotides being added one by one, all at once; the lagging strand is replicated in smaller fragments1. RNA primase is an enzyme that initiates the addition of the first nucleotide on the leading strand, while the DNA polymerase stays at the end of the replication fork, by the split, adding nucleotides in a continuous fashion2. On the lagging segment, small segments of nucleotides are added onto the strand called Okazaki fragments; they are synthesized in the 5’ to 3’ direction away from the replication fork and the fragments are then stitched together by DNA ligase; replication is discontinuous Semiconservativereplication Parental strandsDaughter strandsII. Transcriptiona. Transcribes genetic information from DNA to RNAi. This message, RNA transcript, is used in various cell functions, such as production of proteins necessary for cellsb. Three main steps to transcriptioni. RNA polymerase attaches to the promoter region of the DNA and transcribes itii. Elongation 1. Transcription factor proteins unwind the DNA and allow RNA polymerase to copy a single strange of DNA into a single strand of mRNA, as a template- the antisense strand; the other strand which was not transcribed is the sense stranda. DNA and RNA share the same nucleotide bases, except while DNA has A, G, C and T, RNA has A, G, C and U, which in turn pairs with the A during transcription iii. Termination1. RNA polymerase goes along the DNA until the terminator sequence, where it detaches from the DNA, releasing the mRNA2. The mRNA goes to the cytoplasm to perform translation5′3′3′3′5′5′RNA primerPrimaseHelicaseDNA polymerase IIISingle-strandbinding proteinRNA primerLeading strandLagging strandIII. Translation a. Conversion of the mRNA to amino acids to for the proteinsi. Initiation begins small ribosomal subunit binds to a sequence of the mRNA chainii. An initiator tRNA binds at the same time to a specific codon on the mRNAchain as welliii. The large ribosomal subunit joins the complex and the tRNA binds on the P site, leaving the A siteiv. A new tRNA binds to the A binding site whence it recognizes the specific codon sequence of mRNAv. Peptide bond forms between the two amino acids attached to the tRNA at the P and A binding sitesvi. Elongation occurs as the ribosome moves along the mRNA and the tRNA at the P site releases, allowing for the tRNA at the A to move to the vacant P site; this continues as the chain of amino acids growsvii. Until the termination codon is reached on the mRNA by the ribosome, this cycle of elongation will occur, until it then detaches all