BIO130 Section One Guide (6A)

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University of Toronto St. George
Kenneth Yip

Chapter 6 How Cells Read the Genome: From DNA to Protein - Proteins working closely with one another often have their genes located on different chromosomes, and adjacent genes often encode proteins that have little to do with each other - DNA uses RNA as in intermediary to direct protein synthesis o When the cell needs a particular protein, the nucleotide sequence required is first copied into RNA (transcription) and then these RNA segments are used directly as templates to direct the synthesis of the protein (translation) o DNA RNA protein From DNA to RNA Portions of DNA Sequence Are Transcribed into RNA - Step 1 is to copy a gene into an RNA nucleotide sequence (transcription) - RNA is a linear polymer like DNA made of A, U (not T), G, C nucleotides linked together by phosphodiester bonds o Differ from DNA in that the nucleotides are ribonucleotides; they contain the sugar ribose rather than deoxyribose - RNA is typically single-stranded, but may fold onto itself to have double-stranded sections Transcription Produces RNA Complementary to One Strand of DNA - Transcription begins with the opening and unwinding of a small portion of the DNA double helix - One of the two strands acts as the template for the synthesis of an RNA molecule o Nucleotide sequence of the RNA chain is determined by complementary base- pairing between incoming nucleotides and the DNA template o Incoming ribonucleotides are covalently linked to the growing RNA chain - **unlike DNA replication, RNA does not remain hydrogen-bonded to the DNA template strand o Instead, as the RNA chain forms, the DNA helix reforms - RNA molecules are considerably shorter than DNA molecules - RNA polymerases enzymes that perform transcription o They catalyze the formation of phosphodiester bonds linking nucleotides together o Unwinds DNA just ahead of the active site for polymerization o Its substrates are ATP, CTP, UTP, and GTP - Many RNA copies can be made of a single gene on a DNA strand - Differences between RNA and DNA polymerase:
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