Bacterial Genetics Flashcards
Bacterial populations are clonal, meaning that in the absence of mutation or gene exchange, all descendants of a cell are
Genetically identical
Rare genetic events that have a substantial probability of occurrence
Corollary
In Neisseria gonorrhoeae, resistant mutations accumulate with the use of
Penicillin
What is the concentration of penicillin required to inhibit the growth of Neisseria gonorrhoea?
0.015 ug/mL
Bacteria can also acquire drug resistance from
Another source
Encodes an enzyme that hydrolyzes penicillin
Plasmid-based gene
Bacterial genomes are typically made up of a single
Circular DNA molecule
A few species of bacteria have
Multiple or linear chromosomes
Makes all required compounds from glucose, multiplies outside host
E. coli (4700 genes)
Obligate parasite, requires many small molecules for survival
Haemophilus (1743 genes)
No cell wall, requires nearly all small molecules for survival
Mycoplasma (470 genes)
Accessory genetic elements are common in
Bacteria
What are 5 accessory genetic elements that are common in bacteria?
Plasmids, viruses (i.e. bacteriophages), Insertion sequences, Transposons, and pathogenicity islands
Chromosomes, plasmids, and viruses have sites for initiation of
DNA synthesis
Molecules with these sites are classified as
Replicons
Many replicons also have sites for partition of replicated DNA into
Daughter cells
Are not replicons and only replicate when integrated into one
Insertion sequences, transposons, and pathogenicity islands
Mostly circular DNA
-there are many types
Plasmids
Genetic parasites that inject genomes into the bacterial cell to use its machinery for their replication
Bacteriophages
Release progency by lysis of the cell that they took over
Virulent (or lytic) bacteriophages
Insert genomes into bacterial chromosome and replicate as part of it
Temperate bacteriophages
Viruses that integrate their genome with bacteria are called
Proviruses or prophages
Later, the provirus can then excise from the chromosome, replicate, and
Lyse the cell
Non-viral genes can become incorporated into a
Provirus
Expression of most genes in a provirus is blocked by a
Provirus-endocded repressor
Virulence genes, especially toxins, are often found in
Proviruses
Can move from one location to another in DNA
Insertion sequences
Insertion sequences contain only the machinery for their own movement. This is the gene for
Transposase
An enzyme that catalyzes movement
Transposase
Insertion sequences can move because inverted repeats at the termini of the transposase gene are recognized by
Transposase
A sequence of nucleotides that is the reverse complement of another sequence located farther downstream
Inverted repeat
Resemble insertion sequences, but contain genes unrelated to transposition
Transposons