Lecture 11 Flashcards
What is a problem with ordering via transduction mapping? How is this helped?
Mapping by transduction doesn’t allow us to easily tell the order of markers in the first experiment, we must select for a different marker in order to determine marker orders.
What are the two major split ups of the bacterial genome?
The core bacterial genome is the chromosomes, essential genes and is shared via vertical transmission. Most bacterial DNA comes from the accessory genome though, these are the: plasmids, transposons, ICEs (integrative and conjugative elements), lysogenic phages, non-essential genes, adaptive genes and are shared via horizontal transmission.
What are plasmids?
Plasmids are extrachromosomal genetic elements, they are capable of autonomous replication and are not essential to cell under all circumstances (not for day-to-day survival). They contribute to bacterial evolution and genetic plasticity, are highly important in recombinant DNA technology and can encode important phenotypes.
What are some plasmid encoded phenotype examples?
Examples of plasmid encoded phenotypes are: F factor, antibiotic resistance (R plasmids), antibiotic and bacteriocin synthesis (and resistance), irulence and symbiotic nitrogen fixation.
What must plasmids do in order to be successful?
Most plasmids are essentially molecular parasites as they are often of no use to their host, in order to be successful they must: replicate, segregate (needs to ensure each saughter cell reacieves at least one copy), keep the host happy (not huge metabolic load, large plasmids have low amounts of copies (1-5), small plasmids have large amounts of copies (10-50)), keep host under control (kill cells foolish enough to remove them, addiction systems) and be able to spread (either through conjugation or other methods).
How do high copy and low copy plasmids ensure the daughter cells get at least one copy?
High copy plasmids make large number of copies to ensure that random chance makes it unlikely to not be inherited by both daughter cells, low copy plasmids have special mechanisms to ensure daughter cells get at least one each. This partitioning by low copy is typically done by a protein finds both plasmids, another protein then comes along and elongates by adding monomers, this elongation ensures they will be on opposite sides of the cell and depolymerization can then occur, with cell division then ensuring one in each daughter cell.
