Which of the following events is least likely to result in a genetic change in a bacterium?

Question

A.  pilus formation
B.  conjugation
C.  specialized transduction
D.  generalized transduction
E.  natural transformation

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
 
Gather Content
· What do you already know about horizontal gene transfer? How does it relate to the question?
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

A.  pilus formation

Clarify Question
· What is the key concept addressed by the question?
        o The options list various processes a bacterium could undergo. Which process is least likely to result in the bacterium getting new DNA?
· What type of thinking is required?
        o This question is an “evaluate” question. You need to judge the probability of each option resulting in genetic change. You should then pick the option that has the LEAST probability of the bacterium getting new DNA.
 
Gather Content
· What do you already know about horizontal gene transfer? How does it relate to the question?
        o Horizontal gene transfer occurs when the DNA from a donor cell is inserted into the DNA of a receiving cell. This DNA could be new or could look like the original DNA. There are three types of horizontal gene transfer: conjugation, transformation, and transduction.
        o Conjugation occurs when a donor cell attaches to a recipient cell using a sex pilus. The donor cell then transfers a copy of the F-plasmid to the recipient cell.
        o Transduction occurs when a virus accidentally picks up DNA from an infected bacterium’s chromosome. It then inserts this DNA into the next bacterium that the virus infects.
        o Transformation occurs when a bacterium picks up DNA from its environment, either by taking in free-floating DNA or by taking DNA from a cell it just consumed using phagocytosis. The bacterium inserts this segment of DNA into a similar region in its own chromosome. Sometimes this new DNA contains new genes. These new genes could be beneficial or detrimental.
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Look at each option and picture the process in your mind. It may help to draw cartoons of each process. Which ones involve DNA transfer? Which direction is the DNA moving? What is the probability that the recipient cell will get any DNA at all?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked you to determine which of the options would be the least likely to result in a change in the bacterium’s genotype.
        o If you got the correct answer, great job!
        o If you got an incorrect answer, where did you get stuck?             · Four of the options discuss processes of horizontal gene transfer. All four have relatively the same probability of a bacterium getting new DNA.
            · “Pilus formation” is different. Bacteria can form pili that are not sex pili. These pili are used for movement or to pull the bacterium closer to a surface. If it is a sex pilus, it will only form on a donor cell, and donor cells do not get new DNA.