Chapter 7 Flashcards
(170 cards)
What are common allelic variations among bacteria?
Sensitivity to antibiotics
Differences in their nutrient requirements for growth
What is genetic transfer?
The physical transfer of genetic material from one bacterial cell to another.
Why is genetic transfer an advantage?
It enhances the genetic diversity of bacterial species.
What is an example of the advantage of genetic transfer?
A bacterial cell carrying a gene that provides antibiotic resistance may transfer this gene to another bacterial cel, allowing that bacterial cell to survive exposure.
What is the first mechanism for transfering genetic material?
Conjugation
What is conjugation?
A form of genetic transfer between bacteria that involves direct physical interaction between two bacterial cells. One bacterium acts as donor and transfers genetic material to a recipient cell.
What is a second mechanism of genetic transfer?
Transduction
What is transduction?
A form of genetic transfer between bacterial cells in which a bacteriophage transfers bacterial DNA from one bacterium to another
What is the third mechanism for genetic transfer?
Transformation
What is transformation?
- when a plasmid vector or segment of chromosomal DNA is introduced into a bacterial cell
- When a normal cell is converted into a malignant cell.
A form of genetic transfer that involves the uptake of a fragment of DNA from the environment is called
a. conjugation
b. transduction
c. transformation
d. all of the above.
c. transformation
Who first discovered bacteria’s transfer of genetic material? When?
Joshua Lederberg
Edward Tatum
1946
What is a minimal medium?
A type of growth medium for microorganisms that contains a mixture of reagents that are required for growth; nothing additional has been added.
What is a auxotroph?
A strain that cannot synthesize a particular nutriet and needs that nutrient supplemented in its growth medium or diet.
What is a prototroph?
A strain that does not need a particular nutrient supplemented in its growth medium or diet.
What did lederberg and Tatum study?
E. coli and putting bacteria in an environment which lacks the needed nutrients for half of the bacteria but, is perfect for another. They observed the transfer of genetic material.
Describe how gene transfer can explain the growth of colonies on the middle plate?
To grow, the colonies must have functional copies of all five genes. This could occur by the transfer of the met+ bio+ genes to the met- bio- thr+thi+ strain or the transfer of the thr+leu+ and thi+ genes to the met+bio+thr-leu- strains
In 1950, what did Bernard Davis do?
conducted an experiment showing that two strains of bacteria must make physical contact with each other to transfer genetic material.
How did Bernard David conduct his experiment?
Used a U-tube at the bottom is a filter with pores small enough to allow the passage of genetic material, but too small to allow bacteria cells to pass. One side was one bacterial strain with a combination of nutritional requirements, the other had a different strain requiring nutritional requirements. It showed no bacteria colonies grew on the plate, they needed direct contact to grow.
In Bernard Davis study, what was the purpose of using a U-Tube?
Because bacteria are too large to pass through the filter, the aparatus can determine if direct cell-to-cell contact is necessary for gene transfer to occur.
What is an F factor?
A fertility factor found in certain strains of bacteria in addition to their circular chromosome. Strains of bacteria that contain an F factor are designated F+; strains without F factor are F-
F factor carry what?
Several genes that are required for conjugation to occur.
Would a circular DNA molecule be found in an F+ or F- cell?
F+
What is sex pili?
A structure on the surface of bacterial cells that acts as an attachment site to promote the binding of bacteria to each other.