Describe the basic structure of DNA
- Double helix stranded, H-bonds between bases
- Sugar backbone (deoxyribose)
- Phosphate group
- Nitrogenous base: adenine, guanine, cytosine, thymine
Describe the basic structure of RNA
- Sugar backbone (ribose)
- Phosphate group
- Nitrogenous base: adenine, guanine, cytosine, uracil
- Single helix strand
Describe the basic structure of proteins
- Amino acid subunits: amino group, carboxyl group, functional group
- Amino acids joined by peptide bonds
Define transcription
Process where information in DNA is copied into mRNA for protein production
Define translation
- Conversion of genetic material in mRNA into protein using ribosomes and tRNA.
- Sequence of nucleotides in mRNA transcripts and determines the exact sequence of amino acids in proteins
Describe a typical bacterial chromosome
- One circular, double-stranded chromosome
- DNA
- Millions of base pairs
- No nuclear membranes
- Haploid
What are the different types of mutations?
substitution, insertion, deletion
What is substitution?
When the incorrect nucleotide is transcribed (A instead of C)
What is insertion?
When a nucleotide is inserted (becomes longer)
What is deletion?
When a nucleotide is taken away (becomes shorter)
What are the consequences of mutations?
- silent (doesn’t affect or change amino acid)
- missense (structure/function changed)
- nonsense (Result in stop codon - premature
truncation of proteins)
What are mobile genetic elements?
- Pieces of DNA which can be transferred between bacterial cells
- Contribute to genetic diversity by: introduction of new genes into genome OR by altering gene expression downstream of insertion site
- Altering genetic environment leads to resistance or increased pathogenicity and virulence
What are the transposable elements?
Insertion sequences (jumping gene), integrons and transposons
How do insertion sequences work?
- Move from one position on a chromosome to another, when it moves it can be retained or lost at original position
- If inserted in gene, can inactivate expression
- Contains: transpose gene (enables to move), regulatory gene (induces or inhibits transpose gene), and inverted terminals (repeats &enables recombination)
How do transposons work?
- Contains genetic materials often including virulence and antibiotic resistance genes, bracketed by IS
- Transported between bacteria on conjugate plasmids
How do integrons work?
- Capture and carry genes
- Allows bacteria to adapt and evolve rapidly
- Integrase gene allows site specific recombination and integration of integron at a recombination site
What are characteristics of plasmids?
- Extra-chromosomal circular double stranded DNA
- Smaller than chromosome
- Exists and replicates independent of chromosomes
- Multiple plasmids per cell
- Non-essential but improve survival under stress
How do plasmids work?
- Can spread via conjugation to other bacteria
- Can encode variety of genes, including antibiotic
resistance and virulence genes
