Chapter 16- Genetics Flashcards
what is Recombination
Process in which one or more nucleic acids are rearranged or combined to produce a new nucleotide sequence (recombinants)
what is a mutation?
heritable changes in DNA sequence.
what is vertical gene transfer?
transfer of genes from parent to progeny. In Eu- crossover of chromosomes results in recombination
what is horizontal gene transfer?
Genes from one independent, mature organism to another
what are the types of HGT?
transformation- DNA acquired from environment
conjugation- DNA transferred from donor cell
Transduction- DNA transported in a bacteriophage
Transposons
mobile genetic elements (DNA sequences
coding for enzymes that allow them to “jump”) (in conjugation)
what is a conjugative plasmid?
usually DNA transferred in conjugation-
small DNA molecules that can exist independently of the host with replication properties
what is the F factor?
plasmid that acts as a fertility factor, enabling conjugation
F factor integration
F+ (donor) attaches to F- and they mediate recombination with the host cell chromosome
episome
can exist outside the cell or be integrated
sex pilus
used to establish contact between F+ and F− cells
Type IV secretion
system assembled by F+ cell
what is rolling-circle replication
one strand of DNA from the F plasmid is nicked and the 3’ OH end is extended by replication enzymes and the 5’ side is a tail
Hfr conjugation
Donor transfers chromosomal
genes with great efficacy but
does not change recipients into
F+ cells
Hfr strain
-donor
- F factor is in chromosome, rather than plasmid. (Whole host chromosome is
transferred and remains
connected for a period of time)
F’ conjugation
F factor can leave bacterial chromosome
(from Hfr strain) and resume status as
autonomous plasmid
F’ plasmid
New plasmid that is genotypically
distinct from original F factor (but
has all necessary fertility factor
genes)
Virulent bacteriophages transduction
- Can carry out the lytic cycle.
- Host cell is lysed so the virus can be released to infect new host
cells.
Temperate bacteriophages transduction
- Lysogeny—relationship between virus and host cell.
- Developed by inserting genome into a bacterial chromosome
generalized transduction
- any part of bacterial genome can be transferred
- occurs during lytic cycle
- during virion assembly, genomes
specialized transduction
- occurs in lysogenic cycle
- When a prophage is induced to leave a host, excision is carried out improperly.
- Resulting phage genome has portions
of bacterial chromosome next to the integration site.
core-genome
set of genes found in all members of a species (Often thought of as the minimum genes needed to survive)
pan-genome
every gene in a strain of a species. (More recently acquired genes that enable microbial colonization of new niches.)
transmission of drug resistance
Resistance genes exist in nature to protect antimicrobial producing microbes from their own antimicrobials
