Lecture 10 Flashcards
What is the exogenote and endogenote and how many cross overs are required?
The exogenote is the part of the DNA from the Hfr donor recipient. The endogenote is the DNA from the F- recipient (complete genome). The exogenote will not be full but the endogenote will be, thihs means they are merozygote(partial diploid). If they recombinate at only one point a linear nonviable strand will be created. Hence an even number of crossovers are required (one on either side of the gene to be swapped), in order to create the circular viable strand(incorporating the DNA) and a non viable linear fragment.
Why is high resolution mapping done and how?
High resolution mapping by recombination frequency is done to determine the distance between markers, interrupting mating will determin the order. More recombination will occur with markers closer to the origin, therefore we can select for the last marker (therefore choosing the distal crossover point) to enter then screen for the earlier markers, selecting for the last marker is done by time of entry.
The frequency of different recombinant classes will depend on the distance between each pair of genes, the closer to the last marker the more likely each marker will be in the recombinant.
What are the key parts about the E.coli chromosome?
The E.coli chromosome has 48 transposable elements, genes of related function are often clustered together into operons, the pathogenic isolates differ from benign isolates by presence of plasmids and clusters of horizontally acquired virulence genes(“pathogenicity islands”) on their chromosomes.
How does generalised transduction occur and what is key?
Generalised transduction occurs via: Donor bacterium gets infected by phage DNA, breaks up the bacterial chromosome and produces phage proteins which get assembled. Phages may accidentally grab a fragment of bacterial DNA, this will then be injected into a recipient and combined via recombination. The amount of DNA that can be transduced is limited by how much DNA can be packed in a phage head, this varies. The phage host specificity is determined at least in part by cell surface receptors.
Whaat is special about mapping by transduction?
Mapping by transduction can be done, this will mean that the markers are on the same fragment and distance can also be done based on percentages as with conjugation.
