need help with your account or subscription? click here to email us (or see the contact page)
join telegramNEW! discord
jump to exam page:
search for anything ⋅ score predictor (โ€œpredict me!โ€)

Retired NBME 16 Answers

nbme16/Block 3/Question#20 (reveal difficulty score)
An investigator is studying strains of ...
Natural transformation ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
tags:

 Login (or register) to see more


 +6  upvote downvote
submitted by โˆ—itsalwayslupus(48)
get full access to all contentpick a username

Natural transformation is when bacteria take up naked bacterial chromosomal DNA in their environment (usually from cell lysis). A cell "lysate" is what remains of bacterial genes when the bacteria is dead (can be extracted from bacteria, as shown here). The SHiN bugs all can undergo transformation. You know it is transformation even without knowing which bugs can do so because it doesn't take up the DNA when DNase is added (it kills any free environmental DNA in the lysate)

get full access to all contentpick a username
topgunber  just wondering why is plasmid transfer not a good option??? +2
m0niagui  Transduction requires the presence of a bacteriophage virus. Plasmid transfer requires two different live bacteria, point mutations will not occur across colonies so uniformly and neither will strand mispairing. +1
shakakaka  @topgunber I think DNase wouldn't stop the process in case of plasmids +4
topgunber  you're right in that DNAse wouldn't be able plasmids in living cells because they are inside the bacteria (same with their nuclear dna). Since living cells use sex pilli to transfer plasmids yes, DNAse wouldn't stop plasmid transfer. Key there is they had to be living. I do think a dnase can break down a plasmid in extracellular solution though (its just another piece of dna). +1
l0ud_minority  Key is heat-killed here and if you remember Griffith's Experiment it relates to transformation +



Must-See Comments from nbme16

bingcentipede on Cerebral edema
zincy7 on Gastrin
cassdawg on Kidney
medninja on Lysosomes
cassdawg on Sildenafil
cassdawg on Feces-contaminated soil
cassdawg on Presence of an internal ribosome entry site
cassdawg on Peutz-Jeghers
hungrybox on Induction of cytochrome P450 enzymes that ...
andro on Antagonizes VLDL-cholesterol secretion
bingcentipede on Decreased function of Na+โ€“K+ ATPase
bingcentipede on Glyceraldehyde-3-phosphate dehydrogenase
cassdawg on 46,XXY
bingcentipede on Grade 4/6, holosystolic murmur heard best ...

search for anything NEW!