Microbial Genetics

• Genetics - the study of heredity, genes and the

  mechanisms that they carry this

  information. It involves processes like replication and expression.
• Genome - Complete genetic information of the cell
• Chromosome - The structures that are composed of DNA that

  carry the hereditary information
• Gene - Segments of the chromosome that code for a

  specific product (usually a protein)
• Genomics - Sequencing and molecular characterization of

  genomes
• DNA (deoxyribose nucleic acid) - is a nucleotides that has three components which are phosphate, deoxyribose sugar, nitrogenous base (Adenine, thymine, cytosine or guanine). It is also bonded by hydrogen bonding.
• Genetic code - Determines how nucleotide sequence is

  converted into amino acid sequences
• Conversion of DNA to proteins:

  Gene on DNA

  Converted to mRNA

  mRNA on ribosome

  tRNA brings amino acids to

  ribosome for protein synthesis
• Genotype - Genetic information of the organism. Information that codes for characteristics

  of the organism
• Phenotype - The expressed or physical characteristics

  of the organism. The expression of the genotype
• Escherichia coli - Bacteria that is commonly found in the lower intestine of warm-blooded organisms. Most E. coli strains are harmless, but some can cause serious food poisoning.
• Shiga toxin-producing E. coli (STEC) - a bacterium that can cause severe foodborne disease. Primary sources of STEC outbreaks are raw or undercooked ground meat products, raw milk, and faecal contamination of vegetables.
• Genetic map or genome mapping - Based on time for chromosome exchanged between two cells genetic techniques to construct maps showing the positions of genes and other sequence features on a genome. Identify the location of a gene on a chromosome and the distances between genes.
• Parental strand - it produced two new “daughter strands” in which each strand acts as template for new strands
• Semiconservative replication - produce two copies that each contained one of the original strands of DNA and one new strand. It is also beneficial to DNA repair.
• Transcription - process of taking DNA code and converting to

  RNA code
• Translation - Converting RNA (mRNA) with tRNA to form

  amino acid sequences and proteins. It occurs at ribosome
• Three types of RNA - mRNA - messenger; tRNA - transfer; rRNA – ribosomal
• Degeneracy Code - Allows for mutations in bacteria
• AUG - starting codon
• Sense codons - Code for amino acids which has 61 codons
• Nonsense codons - Stop codons. UAG, UAA, UGA. It signals end of protein

  synthesis
• Transfer RNA (tRNA) - Anticodon. Complementary to codon. Amino acid attached. Brings amino acid to ribosome
• Exons – Expressed DNA, code for protein

  Introns – intervening DNA, do not code for protein
• Feedback inhibition - stops a cell from performing unneeded chemical reactions. Stops enzymes that are already synthesized
• Bacterial Communication

  A) Autocrine Signaling

  B) Paracrine Signaling

  C) Endocrine Signaling

  D) Direct Signaling

  
• Type of Bacteria

  A) Monotrichous

  B) Lophotrichous

  C) Peritrichous

  D) Amphitrichous

  
• 5 ATP - per peptide bond

  2300 ATP - per typical protein synthesized are

  required.
• Inducible genes - Production of enzymes is regulated and produces inducible enzymes
• Operon model

  
• Promoter region - Region of DNA where RNA polymerase initiates transcription

  Operator region - Go or stop signal for transcription of the structural genes

  Structural genes - Genes for metabolism of lactose
• Parts of the Operon Model.

  A) Regulatory Gene

  B) Promoter

  C) Operator

  D) same

  E) Control Region

  F) Structural Gene

  
• Lac operon - Catabolite repression. Inhibition of the metabolism of other carbon sources by glucose (Glucose effect)
• Mutation - Change in the base sequence of DNA that may cause change in the product coded by the gene.
• Base substitution (point mutation) - AT substituted for CG. mRNA carries incorrect base.
• Mis sense mutation - Base substitution results in an amino acid substitution in protein.
• Non sense mutation - Base substitution creates a nonsense or stop codon. Protein is not produced. Only a fragment of protein is produced
• Frame shift mutation - One or a few nucleotide pairs are deleted or inserted in the DNA. Shifts the translation reading frame. Almost always result in a long stretch of altered amino acids. Inactive protein
• Huntington's disease - caused by the insertion of extra bases into a gene
• Spontaneous mutations - Occur occasionally in DNA replication