FogeltheVogel t1_j69weaz wrote

A few planets is a tiny fraction of the mass of a start system. How exactly is that an example of a galaxy sized structure needing multiple galaxies worth of material?


FogeltheVogel t1_j31jxvf wrote

Yes. That's why getting soap in an open wound is painful, and why drinking soap is so dangerous.

However, your outer skin is mostly immune to this as it's not made of living cells, but rather a layer of dead cells that made some structures that resist this before they died.


FogeltheVogel t1_j31j52t wrote

Not easily like with Antibiotics. Antibiotics are like scalpels, they target 1 very specific part of the bacteria and disrupt that part. By changing that part slightly, the antibiotic stops having an effect (or alternatively, they set up systems to pump the molecules of antibiotics out of the bacteria before they can do harm).

Meanwhile, soap is almost like a fire. It simply rips the entire membrane apart. In order to prevent this, they'd need to fundamentally change how the membrane is constructed. Fundamental changes like that are, while not impossible, basically unheard off in evolution.


FogeltheVogel t1_iy01ut5 wrote

When DNA experiences a double stranded break (the type that CAS9 makes), there are 2 methods a cell has to repair it.

The first is the sloppy one, called non-Nomologous End Joining. The machinery for DNA repair can't really do anything with blunt breaks (the type that CAS9 makes), it needs ends that stick out a bit. Called literally Sticky Ends (if they overlap). Sticky vs blunt ends. So the first step is enzymes that remove some nucleotides from each end to make them sticky. After that, other enzymes come in that take these sticky ends and extend them into each other, repairing the break. The problem here is that some nucleotides get lost, and some random ones are added. This usually breaks the gene. When using CAS9 to knock out genes, this is sufficient.

The second method is what's used here. It's called Homologous Recombination, and it is not always possible to use. In essence, it uses the other chromosome as a template to accurately repair the DNA. Under normal conditions, this can't be used because the other chromosome is not readily available to serve as a template. During CRISPR treatments to insert a new geme, we provide a piece of DNA along with the CAS9 and it's guide RNA. This piece of DNA is the "new" gene, but it isn't incorporated like you originally thought. Instead, it is specifically designed so that the 2 ends of this piece of DNA are perfect matches to the 2 sides of the break made by CAS9. The DNA repair complexes will see thus use this as a template to 'repair' the break perfectly. Only in this case, they include extra nucleotides that were never part of the original strand.

I hope this helps.


FogeltheVogel t1_ixlwx8v wrote

The cells won't instantly die. We're talking about a window of (up to) hours here. And we're also talking about vials containing 1 millilitre of liquid.

In general, you thaw such a sample by simply placing it in liquid water. It'll be thawed in minutes.


FogeltheVogel t1_ixl9uro wrote

Lots of cryoprotectants are toxic to the cells we add to. The trick is that, after adding it to the sample, the sample quickly goes in the liquid nitrogen to freeze. This stops biological activity, which is why the toxic properties of the cryoprotectant don't damage the cells.

After thawing a sample, the cryoprotectant is quickly replaced with regular media before it can damage the sample


FogeltheVogel t1_iurke8y wrote

> However, one of the new cells would still contain the "original" DNA.

This is where your question is based on a wrong assumption.

When a cell divides in 2, it is not the case that 1 daughter cell has the original DNA, and the other has the copy. Instead, DNA is made up of 2 complimentary strands, woven together in a double helix. During replication of the DNA, these strands are separated and a new copy is made against each original. Each daughter cell then gets 1 of those new helixes. Thus, each daughter cell has 1 DNA double helix, that consists of 1 original strand, and 1 new strand that was made during replication of the original cell.

Note that "1 helix" should be multiplied for however many chromosomes a cell has.