Chapter 7 - Genetic Transfer and Mapping in Bacteria Flashcards
Bacteria reproduce by
Binary fission
Crosses are not used in bacterial genetic analysis - instead, researchers use…
Genetic transfer
Viruses that infect bacteria
Bacteriophages
When a segment of bacterial DNA is transferred from one bacterium to another
Genetic transfer
Genetic transfer increases…
Genetic diversity
Three methods of genetic transfer
Conjugation, transduction, transformation
Involves direct physical contact
Conjugation
Involved bacteriophages
Transduction
Involves uptake from the environment
Transformation
When a donor and a recipient cell make contact and a strand of DNA is transferred
Conjugation
When a bacteriophage infects a donor cell and incorporates a fragment of chromosomal DNA into a new phase particle which incorporates DNA through recombination
Transduction
When a bacterial cell dies and releases a fragment of DNA into the environment to be taken up by a neighboring cell and incorporated through recombination
Transformation
Who discovered genetic transfer in bacteria
Lederberg and Tatum
Type of organism that cannot synthesize a particular nutrient and need it in their growth medium
Auxotrophs
Type of organism that makes all its nutrients from components in the growth medium
Prototrophs
Who showed that bacterial strains must make physical contact for transfer of genetic material to occur
Bernard Davis
What is an F factor
Fertility factor
Can all cells act as donor cells?
No
Strains containing an F factor
F+
Strains not containing an F factor
F-
What initiates conjugation?
Contact
What mediates contact between donor and recipient cells?
Sex pili or F pili
What happens after initial contact is made?
Pili shorten, cells get closer, and a conjugation bridge is formed
What recognizes that origin of transfer and makes a cut in the DNA
Relaxosome
After cutting, the relaxosome releases its accessory proteins except for…
Relaxase
When conjugation occurs, the recipient cell acquires…
F factor
What is extra-chromosomal DNA?
Plasmid
Type of plasmid that allows conjugation
Fertility plasmid
Type of plasmid known as R factors that contains genes conferring resistance to antibiotics
Resistance plasmids
Type of plasmid that carries genes allowing digestion of unusual substances
Degradative plasmids
Type of plasmid that contains genes to kill other bacteria
Col-plasmids
Type of plasmid that carries genes to turn bacterium into pathogenic strains
Virulence plasmids
Who discovered high frequency recombination strains?
Luca Cavalli-Sforza
When F factors are excised imprecisely, they are called…
F’ factors
Who demonstrated that conjugation between Hfr and an F- strain involves the transfer of a portion of the Hfr bacterial chromosome?
William Hayes
What determines the starting point and direction of the transfer process?
The origin of transfer of the integrated F factor
Who developed the interrupted conjugation technique?
Elie Wollman
What is the rationale behind the mapping strategy?
The time it takes genes to enter the recipient cell is directly related to their order along the bacterial chromosome
The order of genes along the chromosome can be deduced by determining…
The time various genes take to enter the recipient cell
The distance between genes is determined by comparing…
The times of entry during an interrupted conjugation experiment
During transduction, two different cycles are possible:
Lytic or lysogenic
Who discovered transformation?
Frederick Griffith
What are the two types of transformation?
Natural and artificial
Bacterial cells that are able to take up DNA
Competent cells
Genes that encode proteins
Competence factors
If the transformed DNA is homologous to a region in the bacterial chromosome, it can be incorporated by…
Homologous recombination
The process in which an organism receives genes from another organism without being a direct offspring
Horizontal gene transfer (conjugation, transformation, and transduction are examples)
Horizontal gene transfer has dramatically contributed to…
Acquired antibiotic resistance
