nbme 3 form 1 - ashy

[ArchivalUser]

Bacterial strian X is resisitant to ampicillin nad sensitive to gentamycin. Bacterial strain Y is resistant to gentamycin to ampicillin. Bacterial strains X and Y are grown in mixed culture in medium without antibiotics, then the culture is plated on medium containing both ampicillin and gentamycin. Bacterial colonies grow on the plates. In a second experiment, DNase is added to the mixed culture medium. When this mixed culture is plated on medium containing both antibiotics, no colonies grow. Assuming thatbacterial cells are impermeable to DNasa, which of the following processes best explains these observations?
(A) Conjugation
(B) Mutatioon
© Transduction
(D) Transformation
(E) Transposition

[ArchivalUser]

AAAA

[ArchivalUser]

Hi Ashy,

I too just did these Qs just today.
I have a Q if you can explain to me..
NBME 3, block 1, Q 17.
Do you think youcan explain how to go about answering it?

thanks.

[ArchivalUser]

Even I though it's A , but the answer key gives D, I mean offline .. Anyone can confirm

[ArchivalUser]

Hi Ashy,

What they are asking here is when does DNA has to come in contact with DNAse (i.e. medium or out of the cell). The DNAse is in the medium and only in transformation DNA has to go through the media where the DNAse will degrade it and the bacteria wont get the resistance gene to survive.

Good luck!

[ArchivalUser]

its DDD only TRANSFORMATION.. bacteria picks up dna from outside. but when its broken down by DNAse then it cannot convert..!!