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Microbial Genetics - Coggle Diagram
Microbial Genetics
Structure of DNA
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The double helix structure of DNA was determined by James Watson + Francis Crick, with help from Rosalind Franklin's findings.
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DNA Structure
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The strands are directional & antiparallel, meaning they run in opposite directions (5' to 3' and 3' to 5').
The 5' end has a phosphate group, while the 3' end has a hydroxyl group.
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Mutations
Frameshift Mutation - occurs when one or more nucleotide pairs are deleted or inserted in the DNA, results in an inactive protein.
Spontaneous mutations - occur in the absence of a mutagen, due to errors in DNA replications. Spontaneous mutation rate is about 1 in a million (10⁻⁶).
Mutagens - agents like chemicals or UV light that cause mutations, increase the mutation rate by 10 to 1000 times.
Mutations can be: Silent, Harmful, beneficial
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Transcription
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Elongation: RNA polymerase synthesizes mRNA in the 5’ to 3’ direction, adding complementary nucleotides (A, U, C, G).
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The Operon Model
Inducible operon- the default state is for a regulatory gene to produce an active repressor protein that binds to the operator, preventing transcription.
Repression - type of regulation that inhibits gene expression, often in response to an overabundance of an end product. It is mediated by repressor proteins that block transcription.
Operon - consists of a promoter, an operator, and structural genes.
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Gene Transfer
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Horizontal Gene Transfer: Genes are passed to other microbes of the same generation. This involves a donor cell and a recipient cell.
Plasmids & Transpoons
Plasmids
Self-replicating, circular pieces of DNA.
Resistance (R) factors - plasmids that carry genes making the cell resistant to antibiotics or heavy metals.
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Transposons
Small pieces of DNA that can move from one region of a chromosome to another, or to a plasmid.