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Lecture 2

Week 2 microbio.docx

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York University
BIOL 2900
Malini Persaud

9Week 2- microbiology - proteins are responsible for most of the activity in the cell - phenotype: physical features of the cell or organism Proteins - amino acid language. - major classes of proteins: enzymatic, regulatory (able to tell DNA polymerase to start from here), structural (responsible for the structure of the cell or cytoskeleton of an organism, not regulatory just proteins that gives us shape) - amino acids are the building blocks of proteins and protein synthesis ( AA has carboxyl, nitrogen group. Some are (+) and (-) charged, some are polar and nonpolar molecules. (know peptide folding so like alpha and beta) Translation: Process converting info stored in nucleid acids sequences into proteins - Genetic code: the ribosome’s read mRNA sequences in 3 base codons. mRNA the template that’s used to specify amino acid sequence. - ribosome’s: a complex of proteins and rRNA molecules - tRNA: small (70-80 nucletide) RNA molecules that serve as adapters between codons in mRNA and amino acids. tRNA anticodon recognize the codon in mRNA. The hydrooxy (3’) end of ach tRNA is linked to the carboxyl group of a specigic amino acid. Serine codon: UCA. Genetic code A universal code that is sued in the nuclear genome of most organism. COmplementrary anticodons are present in tRNA molecules, which are specifically linked to amino acids. (genetic engineering is putting human dna into bacteria for replication) - With 4 bases in RNA and 3 base codons, there are 64 possible codons, but only 20 amino acids. Thus, the genetic code is degenerate, where some amino acids are specified by more than one codon. (upto 6). - 3 stop codons, to terminate protein synthesis. Protein translation Polyribosomes: are strings of ribosome, assembled along an mRNA to increase the rate of protein production. Proteins are still made by starting from the 5’ end and finishing at 3’ end with the finish product which is protein. - so there are many ribosome’s in a cell that make protiens?:S Recombination of DNA - recombination is like genetic engineering. Human RNA injected into bacteria. For example, insulin and cogulation factors - watch video on this. Restriction enzyme, (sticky end cause they can be paired with something similar), then DNA ligase will come and glue it together, - expression vector (promotoer to make mRNA, combines to ribosome, start codon, then coding region, then you will get a protein in the culture medium. tRNA have anticodons and mRNA has codons Mutations - In the living cell, DNA undergoes frequent chemical change, especially when its being replicated. Most of these changes are quickly repaired. Those that are not result in a mutation, then it can be expressed someway in your body. Thus mutation is a failure of DNA repair. Molecular basis of mutation - mutation is any change in an organism’s DNA sequence - DNA mutations affect phenotype only when the mutation is expressed (DNARNA protein), and the resulting protein functions abnormally. Not all mutations affect protein’s ability to func and thus don’t generate a phenotype. - one of the most common type of mutation is point mutation, a change in a single nucleotide. Silent mutation: don’t change the amino acid sequence of the protein is known as silent mutation. When one letter changes in the codon but it still codes for the same amino acid. For ex: CGG would turn into CGC but both of them still vode for ARG. Missense Mutation: its like silent mutation except when the change is made, the new codon codes for a new codon. For ex. TCG codes for SER but with a change in the codon to TTG, it codes for Leu. (it makes a new protein sequence Nonsense Mutation: a mutation that creates a new stop codon. For ex. ATG for Met and changes to ATT which is a stop codon. Insertions and deletions of A.A - point mutation is subtition for one of the codons. For ex.The Bat saw the Dog from the Cat saw the Dog - deletion: the ats awt hed dog (loss of C) insertion: the CMA tsa wth edo G (insertion of M) Frameshift mutation** Consequence of mutation - the activity of the protein is reduced. Genetic disease: sicked cell disease anemia (one change in AA and then one change in protein and it alters the shape of the RBC) - many cancers are caused by defective repair of DNA. Stronger activity of an enzyme. The activity of the protein is reduced. Evolution: is the change in the inherited traits of a population of organisms through successive generations. Mainly by changes of DNA sequences: mutations. Chimps and humans are very similar DNA (90% similar). The most intelligent is the one that survives because it can most adapt to change. Cells Cell theory: developed during the mid 1600s. The discovery of microscopy. All living organisms are made of cells. Cells are created by old cells diving into two. Cells are the basic building unit of life. - cells can be unicellular organisms (made up of one cell. For ex. Bacteria, yeast etc..), multicellular (made up of several to billions of cells. For ex. Most plants and animals. These ce
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