4.3 mechanisms of Gene transfer Flashcards
(28 cards)
using DNA binding proteins, the chromosome is organized into a…
nucleoid
genome
complete set of genes within an organism
plasmid
small circles with base pairs of DNA that are separate from the chromosome
what are plasmids also called
chromosomal genetic elements
what does chromosomal genetic elements mean
they encode non essential genes, therefore if daughter cell lacks plasmid, it still viable.
horizontal gene transfer
transfer of genetic information from host organism to another recipient organism
vertical gene transfer
happens every time cell divides, from host organism to its offspring.
vertical transfer what basically happens (mutations)
genetic info in particular cell is replicated and a copy is transferred to the daughter cell.
- if there is a mutation in the original cell’s chromosome or a plasmid, that mutant is passed along to the daughter cell…
what are the three mechanisms that mediate horizontal gene transfer
transformation, transduction, conjugation
basic run down of transformation
cell takes up DNA directly from environment.
– DNA may be incorporated into the host genome or remain separate from the genome as a plasmid.
basic run down of transduction
bacteriophage injects DNA that is a hybrid of viral DNA and DNA from previously infected bacterial cell
basic run down of conjugation
a conjugation pilis draws two cells close enough to form a cytoplasmic bridge, then DNA is transferred in one direction from donor cell to recipient.
– usually the transfer of plasmid
cells are referred to as what.. when they are capable of taking up DNA and being transformed
competent
in naturally transformable bacteria, competence is a regulated multi-step process. explain the steps
– free DNA can be found in the environment
– it is taken and brought into the cell
– DNA can be degraded and used as a source of nutrients or it can. be covered by single stranded DNA binding proteins and then incorporated into the chromosome
– this incorporation is through the function of the RecA protein
plasmid DNA can also be introduced to bacterial cells through transformation (through lab) explain
cells are made competent by treatment with chemicals – plasmid DNA is added to the cells and taken up by them.
what does ‘rec’ mean in RecA
recombination
lytic cycle of transduction
littler bacteriophage injects its DNA into a host cell,
– there, it directs phage replication, and at the end of replication cycle, host cell. DNA is cleaved into short lenths.
– phage DNA or host DNA can be then packaged into a new generation of phages and is released.
what is the transducing particle and what does it do
a functional particle capable of infecting another host cell
– injects into the host cell, not its own genome, but the piece of DNA from the previously infected genome.
transduction part of the transduction cycle
recipient cell is infected by transducing particle, , there will be no virus production bc no virus genome in this cell.
– homologous recombination, incorporation into host’s genome, generating a transduced recipient cell.
the proteins that mediate transfer in conjugation are encoded on..
the very plasmid that will be transferred called an F plasmid
what does the F in F plasmid stand for
fertility
conjugation step 1
sex pilus (F+ donor cell) attaches to recipient cell. the pilus contracts, drawing the cells together to make contact with one another
conjugation step 2
on strand of the F plasmid DNA transfers from the donor to recipient cell through the cytoplasmic bridge
conjugation step 3
donor synthesizes complementary strand to restore plasmid, and the recipient synthesizes complementary strand to become F+ cell with pilus.
