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Chapter25 DNA Metabolism - Coggle Diagram
Chapter25 DNA Metabolism
基本知識
What Is DNA Metabolism
Although DNA provides stable storage of genetic information, the structure is far from static
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Errors that arise during or after DNA synthesis are constantly checked for, and repairs are made.
Segments of DNA are rearranged either within a chromosome or between two DNA molecules (recombination), giving offspring a novel DNA.
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Naming
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Eukaryotic Gene
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In Saccharomyces cerevisiae, gene names typically three uppercase italicized letters followed by a number
Bacterial Protein
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Nonitalicized, roman type
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Eukaryotic Protein
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In S. cerevisiae, the protein has the first letter capitalized followed by two lower case letters, the number, and the letter “p.”
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Bacterial Gene
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Capital letters added to abbreviation reflect order of discovery, not enzymatic order– dnaA, dnaB genes for replication
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E. Coli DNA Replication
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DNA Polymerase III
Complex structure with 10 types of subunits • Two core domains of α ,ε, and θ subunits
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The core domains each interact with a dimer of β subunits that increase the processivity of the complex.
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processivity of DNA Pol III is >500,000 bp because of the β clamps
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DNA Repair and Mutations
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The Ames Test
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Add compound to plate of Salmonella, see if it grows in His-free medium
Colonies (+ test) indicates the compound mutated the Salmonella, restored ability to synthesize His
DNA Repair and Mutations
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Some base changes escape repair, and an incorrect base serves as a template in replication.
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Accumulation of mutations in eukaryotic cells is strongly correlated with cancer; most carcinogens are also mutagens.
There are thousands of lesions/day (unrepaired DNA damage) but only 1/1,000 become a mutation, thanks to DNA repair.
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Types of DNA Damage
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Abnormal bases arise from spontaneous deamination, chemical alkylation, or exposure to free radicals.
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