How would we clone them back?
Part 1- Nucleus RemovalCloning an organism in this case would be the act of creating an organism with the exact same genetic makeup of another. The most common method that people are familiar with, as well as the method that is most relevant in reviving extinct animals would be SCNT, Somatic Cell Nuclear Transfer.
There are two uses for SCNT, one is for collecting stem cells (therapeutic cloning on diagram) (Cloning Fact Sheet 2015) and the other is known as ‘reproductive cloning’ and as it’s name suggests, is what is suggested to be used in the creation of cloned animals. The process of SCNT involves taking a living cell from an animal, removing the cell’s nucleus and transferring it into an egg cell that has had its nucleus removed. The nucleus is important because it's what contains the genetic information that basically tells what everything should be producing and how much. (Nucleus-Function 2013) The rest of the cell provides things like energy, or building supplies, but it's the nucleus that acts as the control centre for all of that. As such, we can if we remove it, and put it in another cell, it should theoretically produce cells exactly the same as the animal that it came from. So first we'll take a look at the process for removing the nucleus. As we see in the image to the right, A is the cell, B is a suction pipette that is holding the cell steady and C is the glass needle that will do the removing. The cell is around 1/10th of a millimetre wide, so the process is monitored by microscope. In step 2, we see the needle entering the cell, and removing the nucleus. In step 3, this is completed, and the nucleus the glass needle holds is ready to be put into an empty egg cell. Part 2- Using the nucleus to clone |
After the nucleus from the animal going to be cloned is removed, we move onto the next step, which is taking that nucleus and putting it into an egg cell that has had it's nucleus removed. This egg cell, if it was normal cloning, would be sourced from an animal of the same species. Seeing as extinct animals have no living animals to source egg cells from, the cell may come form another species most similar to it. For example, elephants if you're cloning a mammoth.
What we have is an egg cell, with a complete nucleus inside. Which is basically a fertilized egg cell. With some form of stimulus usually an electric shock, the egg cell will start to divide, exactly like if it was a normal fertilized cell. This is allowed to split on it's own until it becomes an embryo. The diagram is not quite accurate, as it names this stage as "Clone" and shows a lot less cells than an embryo would have. "Embryo" is the stage just prior to when cells will start specializing. For example, some will become skin cells, some muscle, some teeth, etc. Therapeutic cloning, as stated previously, relates to using those cells capable of becoming anything. We're interested in reproductive cloning. As shown, the embryo gets placed into a surrogate mother, which will carry the clone to term like it would any other baby. Once again, with extinct animals we run into the problem of not having living animals to work with. So we solve it once again, by using another animals which is genetically similar to the extinct one. (Tanya 2013) By doing this we are capable of resurrecting extinct animals. |
How DNA would be obtained.
Part 1- An Overview
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You may have picked up on a problem with what I've been describing so far. That would be, all of that is fine and dandy, but to even get started you need to extract a living nucleus from somewhere. And as has been pointed out many, many times, extinct animals have no living specimens left. There are a few ways around this. We'll start with the easy one, which is: trying to find a living cell still left. If the animal trying to be cloned went extinct recently, there may have been time to preserve a few of their cells, which could be used. Scientists have also been able to successfully use brain cells of mice which had been frozen for 16 years for cloning. (Derbyshire 2008) There is a slight chance, if an animal died in just the right conditions, and was frozen quickly enough, there may remain living cells, capable of being used.
That method is a long shot though, so let's turn our attention to something a bit more reliable; genome sequencing. The essential gist of it, as laid out by the diagram is basically have DNA in small parts, computer analyses each part, computer then scans for similar chains and connect the DNA chain back together. By doing this we obtain the order each DNA base is in. DNA bases are basically little "blocks" of chemicals, and a cell reads them in order to tell what it should be producing.
So in theory, if you placed these little blocks in exactly the order described by your sequencing, you can get the exact code used to create an animal. The important part though, is that a cell doesn't need to be alive for you to sequence it. In fact it can even be a little bit broken up, or damaged. It just means the chain has been pre-broken when you go to sequence it. So when you find a sample of an extinct animal, you don't have to hope a cell has been preserved perfectly, you can just extract what little genetic information you can get from the specimen you have.
That method is a long shot though, so let's turn our attention to something a bit more reliable; genome sequencing. The essential gist of it, as laid out by the diagram is basically have DNA in small parts, computer analyses each part, computer then scans for similar chains and connect the DNA chain back together. By doing this we obtain the order each DNA base is in. DNA bases are basically little "blocks" of chemicals, and a cell reads them in order to tell what it should be producing.
So in theory, if you placed these little blocks in exactly the order described by your sequencing, you can get the exact code used to create an animal. The important part though, is that a cell doesn't need to be alive for you to sequence it. In fact it can even be a little bit broken up, or damaged. It just means the chain has been pre-broken when you go to sequence it. So when you find a sample of an extinct animal, you don't have to hope a cell has been preserved perfectly, you can just extract what little genetic information you can get from the specimen you have.
Part 2- More about Sequencing
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I mentioned in the previous section that a computer "analyses" each individual piece. Here we'll take a closer look at what exactly that means. The machine that analyses a strand of DNA is called a sequencing machine. There are a few types, but the general principle is similar.
We ensure that we have quite a few copies of the strand of DNA we want to analyse first. Usually scientists focus on one particular segment and will copy that several times. This copying is done through a process called PCR. PCR basically is just replicating how a DNA strand would split in real life.
We take the strand we want analysed which we have multiples of due to PCR, and break it up further. These little chunks of DNA get put into our sequencing machine. In our example in the diagram, it has taken the strand, and at the end marked the A base with a red fluorescent dye. The next one that comes through may be only 3 letters long, and we can see that ends in G. It's marked yellow. The one that comes after might be 6 letters long, and we see that ends in T, which is marked in blue. This continues until the ending letter of each strand of DNA has been marked with one of the four colours, corresponding to the four bases. It is then sorted into size order. So the one with 7 bases first, to 6 bases, 5 bases etc. After all that is done, we put it through a laser, which reads what the fluorescent dye at the ends is, and marks it. By doing this we find the order of part of a DNA sequence. (What's a Genome? 2004)
After doing that one strand/segment, we move onto the next. And the next. Until we've sequenced the entire chain. Then it's like doing a jigsaw. A computer reads the order the bases appears in, and tries to match up ones where the same bases appear in the same order. If you're confused, take a look at Figure 3. This ultimately results in us finding the entire genome of a species.
We ensure that we have quite a few copies of the strand of DNA we want to analyse first. Usually scientists focus on one particular segment and will copy that several times. This copying is done through a process called PCR. PCR basically is just replicating how a DNA strand would split in real life.
We take the strand we want analysed which we have multiples of due to PCR, and break it up further. These little chunks of DNA get put into our sequencing machine. In our example in the diagram, it has taken the strand, and at the end marked the A base with a red fluorescent dye. The next one that comes through may be only 3 letters long, and we can see that ends in G. It's marked yellow. The one that comes after might be 6 letters long, and we see that ends in T, which is marked in blue. This continues until the ending letter of each strand of DNA has been marked with one of the four colours, corresponding to the four bases. It is then sorted into size order. So the one with 7 bases first, to 6 bases, 5 bases etc. After all that is done, we put it through a laser, which reads what the fluorescent dye at the ends is, and marks it. By doing this we find the order of part of a DNA sequence. (What's a Genome? 2004)
After doing that one strand/segment, we move onto the next. And the next. Until we've sequenced the entire chain. Then it's like doing a jigsaw. A computer reads the order the bases appears in, and tries to match up ones where the same bases appear in the same order. If you're confused, take a look at Figure 3. This ultimately results in us finding the entire genome of a species.
Part 3- What to do with the Genome?
Great we've got a complete genome of the extinct animal we want to hypothetically clone. It's still not a living nucleus we can put into an egg cell. What do we do? Well, we've got the order the 4 DNA bases have to be in order to make a cell a "extinct" cell. We could just place A, T, C and Gs in the right order and go for it. Except that would be insanely complicated and precise. Let's perhaps get an animal that is already quite genetically similar, and take a cell from them. Once you get this cell, it should be fairly simple to just alter the parts that are different. This means we skip the step of having to "write" in the parts that are shared by both creatures. Once we do that, we'll end up with a living cell, which should be the same as the extinct animal's, and ripe for SCNT. (Resurrection Biology: How to Bring Animals Back From Extinction 2013)