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A codon is a sequence of three nucleotides mRNA is the molecule that presents codons to ribosomes DNA serves as a codon-storage molecule DNA serves as a template for RNA synthesis Ribosomes translate codons, in sequence, into chains of amino-acids (polypeptides)
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A codon is a sequence of three nucleotides • mRNA is the molecule that presents codons to ribosomes • DNA serves as a codon-storage molecule • DNA serves as a template for RNA synthesis • Ribosomes translate codons, in sequence, into chains of amino-acids (polypeptides) • These amino-acid (and RNA) sequences are precisely controlled • Precision is both costly and requires complex machinery to achieve • Once translated, proteins also are often post-translationally modified • Proteins consist of one or more polypeptide Roles of Central Players
The Central Dogma Note “reading frame”:
Transcription: Elongation Note 5’ to 3’ direction
mRNA Maturation (Eukaryote) mRNA carries the genetic code to ribosomes To function, in eukaryotic systems, if first needs to be matured
tRNA tRNAs translate codon sequence into amino-acid sequence
The Genetic Code mRNAs consist of a sequence of nucleotide triplets—codons—that code for amino acids and which together are described as “The Genetic Code” Note the Degeneracy of the Triplet Code But also note the lack of Ambiguity 61 sense codons per 20 amino acids
Aminoacyl-tRNA Synthetase Aminoacyl-tRNA Synthetases are responsible for tRNA’s ability to precisely translate codon-based code into amino-acid sequence
Types of Mutations Mutations are alterations in DNA sequence that result either in modified transcription (since smaller target means less likely) or in modified translation (which we shall dwell upon)
What is Microbiology? Microbiology is the Science that studies Microorganisms. Microorganisms, roughly, are those living things that are too small to be seen with the naked eye. Microorganisms cannot be distinguished Phylogenetically from “Macroorganisms”, e.g., includes fungi as well as bacteria, etc. Microbiology is more a collection of techniques: • Aseptic technique • Pure culture technique • Microscopic observation of whole organisms • etc. A microbiologist usually first isolates a specific microorganism from a population and then cultures it.
Microbes & Ecology • Microbes are produces—they provide energy to ecosystems • Microbes are fixers—they make nutrients available from inorganic sources, e.g., nitrogen • Microbes are decomposers—they free up nutrients from no longer living sources • Microbes form symbioses (such as mycorrhizal fungi associated with plant roots—though these are somewhat macroscopic; also the bacteria found in legume root nodules, etc.) • Microbes serve as emdosymbionts (e.g., chloroplasts and mitochondria)
Microbes in Industry & Health • Industry: Fermentation products (ethanol, acetone, etc.) • Food: Wine, cheese, yogurt, bread, half-sour pickles, etc. • Biotech: Recombinant products (e.g., human insulin, vaccines) • Environment: Bioremediation • Microbes both cause and prevent diseases (for latter: antibiotics are made by microbes and normal flora interfere with pathogen replication) • Microbes produce antibiotics used to treat diseases • The Germ Theory of Disease = Microbes cause disease!
Normal Flora These are the ~harmless microorganisms found on your body. Every part of your body that normally comes in contact with outside world (deep lungs and stomach are exceptions)
Viruses are… “...infectious agents of small size and simple composition that can multiply only in living cells of animals, plants and bacteria [plus fungi & protozoa]. Viruses are obligate parasites that are metabolically inert when they are outside their hosts. They all rely, to varying extents, on the metabolic processes of their hosts to reproduce themselves. The viral diseases we see are due to the effects of this interaction between the virus and its host cell (and/or the host’s response to this interaction).” Encyclopedia Britannica Viruses
The Virion is what defines a virus as a virus • A Virion is the extracellular state of a virus • The job of Virions is to find new cells to infect • As such, Virions are a durable state that is “designed” to attach to susceptible cells • The Virion is then responsible for translocation of the virus genome into the cell • The Virion consists of a DNA (or RNA) genome surrounded by Protein that, in turn, may be surrounded by a Lipid Bilayer • The Protein layer is called a Capsid • The Lipid Bilayer is called an Envelope Virus (Virion Particle)
