BACTE: BACTERIAL GENETICS

• DNA was first discovered by Frederick Miescher in 1869.
• 1920s, Phoebus A. T. Levine discovered that DNA contained phosphates, five-carbon sugars (cyclic pentose), and nitrogen-containing bases
• Rosalind Franklin discovered the helical structure by x-ray crystallography.
• James Watson and Francis Crick, who described the three-dimensional structure of the DNA molecule in the 1950s.
• The helix is a double strand twisted together, which many scientists refer to as a “spiral staircase”
• Nucleotide is a phosphate group
• A nitrogen-containing base, or the “steps,” either a purine or a pyrimidine
• Purine consists of a fused ring of nine carbon atoms and nitrogen.
• two purines in the molecule: adenine (A) and guanine (G)
• Pyrimidine consists of a single ring of six atoms of carbon and nitrogen.
• two pyrimidines in the molecule: thymine (T), DNA only and cytosine (C), uracil U (RNA)
• Nucleotide is a basic building blocks of DNA.
• phosphate attaches to the 4′ carbon of the sugar, and the OH group is attached to the 3′ carbon of the sugar.
• Nucleotide: bases are held together by hydrogen bonds.
• The sequence ACGCT represents different information than the sequence AGTCC
• In RNA, the nitrogenous base thymine is replaced by uracil.
• RNA is a single-stranded and short, not double stranded and long, and contains the sugar ribose, not deoxyribose.
• In a human genome of 3 billion “letters,” even one tenth of 1% translates into 3 million separate lettering differences.
• Polymerase chain reaction technique  - means of amplifying specific DNA sequences and detecting very small numbers of bacteria present in a specimen.
• Genetic tests are necessary to understand the development and transfer of antimicrobial resistance by bacteria.
• Genes- DNA sequence that encodes for specific product.
• Genome – all genes taken together
• Chromosomes – genome organized in discreet elements
• Bacterial chromosome –contains all the genes, double stranded, closed, circular (eukaryotes are linear)
• Replication is the duplication of chromosomal DNA for insertion into a daughter cell.
• Transcription is the synthesis of ssRNA, by the enzyme RNA polymerase, using one strand of the DNA as a template.
• Translation is the actual synthesis of a specific protein from the mRNA code.
• Protein expression also refers to the synthesis of a protein
• Codon is a group of three nucleotides in an mRNA molecule that signifies a specific amino acid.
• Anticodon is the triplet of bases on the tRNA that bind the triplet of bases (codon) on the mRNA
• Bacterial Genome contains all the information needed for cell growth and replication.
• One gene equals one polypeptide - genes are specific DNA sequences that code for the amino acid sequence in one protein
• Plasmids are self-replicating extrachromosomal dsDNA molecules.
• Plasmid is located in the cytoplasm of the cell and are self-replicating and passed to daughter cells, similar to chromosomal DNA.
• Plasmid may sometimes be passed (nonsexually) from one bacterial species to another through conjugation.
• Number: up to 40/cell
• contain 50-100 genes
• Plasmid Types: R factors - contain genes that code for antibiotic  resistance.
• Plasmid Types: Col factors. - Contain genes that code for extracellular toxin (colicines) production that inhibit strains of the same and different species of bacteria.
• Plasmid Types: F (fertility) factors - It promotes transfer of the chromosome at a high frequency of recombination into the chromosome of a second (recipient) bacterial cell during mating.