Lecture 34 Flashcards
What is a genome?
The total complement of genetic information of a cell or a virus.
What is genomics?
The study of all the genes of a cell, or tissue, at the DNA (genotype), RNA (transcriptome) or protein (proteome) level.
What is one of the main reasons to sequence microbial genomes?
The diversity and range of environmental adaptations indicate that microbes hold the solution to many problems which scientists are still seeking solutions.
How do bacterial genomes get preserved in extreme conditions?
The use of spores.
What is an endosymbiont?
A bacteria which is one step above a virus, it still must replicate inside a host cell.
How was the worlds first synthetic organism made?
genome transplantation into a mycoplasma bacterium cell which had had its genome removed.
What strategies do bacteria have to generate diversity? How do they work?
Mutation, transformation, transduction and conjugation.
Mutation: The change in a single nucleotide (e.g substitution, deletion, addition). Occurs spontanteously, randomly (about 1x10^-8) and may be induced by mutagens (e.g UV or chemicals).
Transformation: The exchange of DNA fragments, this can be increases by electroporation (a microbiology technique in which an electrical field is applied to cells in order to increase the permeability of the cell membrane, allowing chemicals, drugs, or DNA to be introduced into the cell). It causes horizontal gene transfer (gene transfer from non parent sources) and is used to generate genetically modified organisms.
Transduction: Genetic exchange via a bacteriophage, this is particularly important for gram positive bacteria. Occurs due to some of the newly produced bacteriophages in the bacterial cell will end up containing host DNA (known as the transducing phage), this phage will then infect a new cell and merge parts of the DNA it contains with its new host.
Conjugation: A process mediated by fertility factors (F) (plasmids), F can incorporate antibiotic resistance genes (An infectious drug resistance). In this the donor cell attaches to the recipient with its pilus, this may draw the cells together, from there one strand of the F plasmid DNA transfer to the recipient, both cells then replicate their lone strand.
How was transformation discovered?
Griffiths living strain R cells and heat treated S cells, the S cells were pathogenic and when heat treated S cells were mixed with living R cells (non pathogenic) they were capable of killing a mouse, once isolated the cells found in the mouse were strain S. This showed that the DNA fragments from strain S joined with strain R.
What are plasmids?
Fertility factors in bacteria which are for genetic exchange, these can transfer multiple drug resistance genes and help influence the virulence of bacteria, these are used in biotechnology to replicate and transfer specific genes.
What happens when a plasmid joins with the chromosome of a bacteria? What does this lead to?
The cells become known as Hfr (high frequency recombinant) cells. These cells can transfer parts of both their chromosomal DNA and the fertility factor and these can then be inserted into the recipient chromosome, this cell will not have fertility factors still and hence will remain F-, despite having recieved DNA.
What are cells with or without fertility factors called?
With are called F+, without are called F-
