Chapter 3 Bacterial Sex Genetics Flashcards
Bacterial chromosome - DS or SS? Haploid or diploid?
DS haploid
4 ways bacteria can exchange genetic fragments
1) transformation
2) transduction
3) conjugation
4) transposon
What is transformation?
When naked DNA fragments from a lysed bacteria bind to a cell wall of another bacterium is taken up and incorporated into the DNA (transformed). Used extensively by scientists working with recombinant DNA
What is transduction?
Occurs when a virus that infects bacteria carries a piece of bacterial DNA from one bacterium to another
What is a virus that infects a bacteria called? What is the difference between a virulent and temperate phage?
Bacteriophage
Virulent - infects, reproduces, lyses and kills the host bacteria right away
Temperate - incorporates into the bacterial chromosomes and waits (time bomb)
What is the integrated temperate phage genome called?
Prophage
What is lysogenic immunity?
The term used to describe the ability of an integrated bacteriophage (prophage) to block a subsequent infection by a similar phage (first come first serve)
Generalized vs. specialized transduction
Generalized - occurs with virulent phages. Adsorption and penetration occur. Destruction of bacterial DNA (some left intact). Phage DNA undergoes replication. Capsids are translated and packed - some packed with the leftover bacterial DNA. Cell lysis occurs liberating the phage (including those packed with bacterial DNA).
Special - occurs with temperate phages. Same process except the DNA is incorporated into bacterial DNA and then spliced out (can splice out incorrectly and include some bacterial DNA).
What is necessary for conjugation?
Self-transmissable plasmid F (+)
What are plasmids?
Circular, DS DNA that lies outside the chromosomes and carries genes (like those for drug resistance)
What is the major mechanism for transfer of antibiotic resistance?
Conjugation
What happens if the extra-chromosomal F plasmid becomes integrated into the neighboring bacterial chromosome?
The cell is then called a Hfr cell (high frequency of chromosomal recombinants)
It can undergo conjugation and the entire DNA is transferred or it may be excised with additional DNA (becomes F prime plasmid)
What are transposons? What is special about them?
Mobile genetic elements that can insert themselves into donor chromosome (phages, plasmids and bacterial chromosomes) without having DNA homology! They do not replicate independently but are copied during their host’s DNA transcription. They may confer antibiotic resistance to a plasmid -> rapid spread!
