MBG exam notes.docx - MBG*2040 Exam Notes Chapter 10 DNA Replication Elements of the replication fork and their functions Topoisomerase an enzyme that

MBG exam notes.docx - MBG*2040 Exam Notes Chapter 10 DNA...

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MBG*2040 Exam Notes Chapter 10: DNA Replication Elements of the replication fork and their functions Topoisomerase : an enzyme that introduces or removes supercoils from DNA (provides an axis for rotation) Helicase (DnaB in E.coli) : unwinding of the complimentary strands of a DNA double helix using energy derived from ATP. DnaC protein is a “loaded factor” that assists in DnaB association at fork. Together they are called DnaB-DnaC complex Primase : catalyzes the synthesis of short (10-60 nucleotides long) RNA strands (primers) that are complementary to the template DNA strands and initiate the synthesis of DNA strands Primosome : a protein replication complex that catalyzes the initiation of Okazaki fragments during discontinuous DNA synthesis. It contains DNA primase and DNA helicase activity RNA Primers : a short RNA sequence with a reactive 3’-OH that can initiate DNA synthesis (Okazaki fragments) along a template. The RNA primers are covalently extended with the addition of deoxyribonucleotides by DNA polymerase III Single-strand DNA-binding (SSB) Protein : a protein that coats DNA single strands, keeping them in an extended state DNA Polymerase III Holoenzyme : catalyzes the addition of deoxyribonucleotides to RNA primers on the lagging strands (works discontinuously by synthesizing Okazaki fragments), and on the leading strands (works continuously) DNA Polymerase I: uses 5’-3’ exonuclease activity to excise the RNA primers and replaces them with DNA chains using the preceding Okazaki fragments as a primer Ligase: an enzyme that joins the ends of two strands of nucleic acids (single- stranded nicks) by phosphodiester linkages Leading Strand: the strand of DNA that is synthesized continuously during replication Lagging Strand: the strand of DNA that is synthesized discontinuously during replication Chapter 11: Transcription Messanger RNAs (mRNAs): intermediates that carry genetic information from DNA to the ribosomes Transfer RNAs (tRNAs): adaptors between amino acids and the codons in mRNA Ribosomal RNAs (rRNAs): structural and catalytic components of ribosomes Small Nuclear RNAs (snRNAs): structural components of spliceosomes Micro RNA (miRNAs): short single-stranded RNAs that block expression of complementary mRNAs Transcription: the first step in gene expression, transfers the genetic information stored in DNA (genes) into messenger RNA molecules that carry the information to the ribosomes, the sites of protein synthesis in the cytoplasm
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Transcription Unit: the length of DNA that is transcribed into a functional RNA molecule. It has one initiation site and one termination site Rho-independent Terminators: contain a GC-rich region followed by 5 or more AT base pairs, with the A’s present in the template strand RNA Polymerase: the enzyme that catalyzes transcription, are complex multimetric proteins Chapter 12: Translation and the Genetic Code Shine-Dalgarno: is a ribosomal binding site (RBS) on the mRNA sequence and it
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