3 ms·

Can the organism replicate the XY pairs during DNA replication (and pass it on to divided cells)? I haven't seen that mentioned, only that it "holds onto it for

by ambrop7 10y ago

Can the organism replicate the XY pairs during DNA replication (and pass it on to divided cells)? I haven't seen that mentioned, only that it "holds onto it for its entire lifespan" which is not clear to me. There's also nothing about the interaction of these pairs with existing mechanisms, like transcription (DNA-->RNA) and translation (RNA-->protein). Could the new new pair increase the space of aminoacids from which proteins can be formed?

oever 10y ago
The XY pairs are not replicated. To replicate them would require the presence of a slew of specialized proteins that can deal with XY pairs. The achievement is that the E. Coli lifetime is not affected. The XY's are probably inserted in a part of the DNA that is not transcribed.
- dnautics 10y ago
  I 150% guarantee you they are in a place that is transcribed. Otherwise there would be no selection pressure to maintain it and the bacteria would kick it out in favor of one of the plain old bases.
- 88e282102ae2e5b 10y ago
  The paper specifically states that these unnatural base pairs were chosen because they can be handled by natural polymerases. Also, the only way to maintain a plasmid over time is to replicate it. In fact, the whole logic of the strategy is to have Cas9 target mutations to the plasmid so that loss of the XY base pair during replication would lead to loss of the plasmid, and thus loss of the antibiotic resistance gene that it also carried.
mvm 10y ago
Artificial base pairs are replicated, it is seen from fig.5 in original article, with nearly 100% retention
88e282102ae2e5b 10y ago
It can replicate them, but the XY pairs are just in a plasmid and not in the genome of the bacteria. They were chosen because natural polymerases could use them. However, there are no corresponding RNA unnatural bases, and there's no tRNA that would recognize that even if there were. So it's going to take a lot more work before you can use these for coding for noncanonical amino acids. This really is just a proof of concept.

by ambrop7 10y ago

oever 10y ago

The XY pairs are not replicated. To replicate them would require the presence of a slew of specialized proteins that can deal with XY pairs. The achievement is that the E. Coli lifetime is not affected. The XY's are probably inserted in a part of the DNA that is not transcribed.

dnautics 10y ago
I 150% guarantee you they are in a place that is transcribed. Otherwise there would be no selection pressure to maintain it and the bacteria would kick it out in favor of one of the plain old bases.
88e282102ae2e5b 10y ago
The paper specifically states that these unnatural base pairs were chosen because they can be handled by natural polymerases. Also, the only way to maintain a plasmid over time is to replicate it. In fact, the whole logic of the strategy is to have Cas9 target mutations to the plasmid so that loss of the XY base pair during replication would lead to loss of the plasmid, and thus loss of the antibiotic resistance gene that it also carried.

mvm 10y ago

Artificial base pairs are replicated, it is seen from fig.5 in original article, with nearly 100% retention

88e282102ae2e5b 10y ago

It can replicate them, but the XY pairs are just in a plasmid and not in the genome of the bacteria. They were chosen because natural polymerases could use them. However, there are no corresponding RNA unnatural bases, and there's no tRNA that would recognize that even if there were. So it's going to take a lot more work before you can use these for coding for noncanonical amino acids. This really is just a proof of concept.