Chapter 8 (bacterial and viral genetics Flashcards
What are plasmids?
small circular pieces of DNA; replicate independently of the genome.
What types of genes do plasmids carry in nature?
Fertility factor, antibiotic resistance, toxin genes
What are episomes?
plasmids that can integrate into bacterial chromosomes.
What are the OriV, OriT, and OriC sequence?
Ori V sequence: will replicate chromosome one time.
Ori T sequence: DNA sequence where transfer of plasmids is initiated.
Ori C:a short sequence of nucleotide that can be recognized as a place to start
What is horizontal gene transfer? How does it differ from vertical gene transfer?
Horizontal gene transfer is independent of reproduction and involves the transfer of DNA between different genomes.
Vertical gene transfer is different because it involves genes transferred from parent to offspring.
Compare and contrast conjugation, transformation, and transduction
Conjugation- takes place when material passes directly from one bacterium to another. Two bacteria lie close together and a connection forms between them. DNA is transferred only from donor to recipient, with no reciprocal exchange of DNA.
Transformation- takes place when a bacterium takes up DNA from the medium in which it is growing.
Transduction- takes place when bacterial viruses carry DNA from one bacterium to another.
Describe the major events associated with conjugation. What protein complexes are involved?
During conjugation, a cytoplasmic connection forms. One DNA strand of F factor is nicked at an origin and separates. Replication takes place on the F factor, replacing the nicked stand. The 5’ end of the nicked DNA passes into recipient cell… where the single strand replicates… producing a circular, double-strand copy of the F plasmid. The F- cell now becomes F+.
What is an Hfr cell? How does it differ from an F+ cell?
an Hfr cell is a high frequency strain, the F factor is integrated into the bacterial chromosome.
Compare and contrast conjugation between: F+/F- cells and Hfr/F- cells.
Conjugating:
F+x F-: two F+ cells
Hfr x F- : one Hfr cell and one F-
What are F’ cells? How can F’/F- conjugation lead to production of a partially diploid cell?
When an F factor does excise from the bacterial chromosome, a small amount of the bacterial chromosome may be removed with it, and these chromosomal genes will then be carried with F plasmid. Cells containing an F plasmid with some bacterial genes are called F prime (F’).
What is a virus?
a virus is a simple replicating structure made up of nucleic acid surrounded by a protein coat.
What is a bacteriophage?
a virus that infects bacteria
What is the difference between a temperate and virulent phage?
Virulent phages: reproduce strictly through the lytic cycle and always kill their host cell.
Temperate phages: can undergo either the lytic or lysogenic cycle.
Compare and contrast the lytic and lysogenic life cycles.
Lytic cyle: a phage attaches to a receptor on the bacterial cell wall and injects its DNA into the cell. Inside the host cell, the phage DNA is replicated, transcribed, and translated, producing more phage DNA and phage proteins. New phage particles are assembled from these components. The phages then produce an enzyme that breaks open the host cell, releasing new phages.
Lysogenic cycle: inside the cell the phage DNA integrates into bacterial chromosome, where it remains as an inactive prophage. The prophage is replicated along with DNA and is passed on when the bacterium divided, certain stimuli can cause the prophage to dissociate form the bacterial chromosome and enter into the lytic cycle.
Compare and contrast generalized and specialized transduction
In generalized transduction , any gene may be transferred.
In specialize transduction, only a few genes are transferred.
