Can we bring back extinct species through cloning?

[Hypercharge]

I've once read an article about a team of scientists who were about to (or wanted to) clone a mammoth with the aid of using elephants.
I have two questions on this topic:
1. Is that possible? (I assume they're using a recovered mammoth genome and in vitro fertilization)
2. If it's possible, how about cloning e.g. a homo erectus?

 

[Ryan_m_b]

The basic idea is to take nuclear material from the organism you are trying to clone, place that in a denucleated ovum of a similar organism and implant the now activated egg into a female. This is far easier said than done however, getting nuclear material from extinct species is extremely hard (and get's harder the older the sample) and AFAIK as yet there hasn't been any success in the mammoth project in extracting enough good quality DNA. Whilst there have been various attempts at this such as cows giving birth to bisons they almost always have failed due to failure of the egg to fertilise and developmental defects in the offspring probably due to the difference in species development.

With regards to your second question it's uncertain, at the moment we don't have any homo erectus DNA (and given that they went extinct nearly 200,000 years ago this will be very difficult) and even if we did the closest related extact species is us and we diverged from erectus nearly 2 million years ago.

 

[Hypercharge]

Gah.
why is it so difficult to recover DNA?
Does it need to be taken from particular cells?
Or is it because of possible errors in the DNA (errors because it was not being "repaired" by the organism)?

 

[epenguin]

Obviously most dead tissue things rots, so you need sources that have been preserved, e.g. mummies or mammoths in permafrost

Then it is chemically degraded over time. Split into short sequences. However PCR, the polymerase chain reaction means in theory you can amplify just one molecule into enough DNA to analyse. So even with a fragmented sample, by overlaps between sequences you may be able to reconstruct quite a long sequence. Among the problems there are contamination by the much more abundant DNA of all sorts of things like bacteria and the humans who have handled the tissues.

DNA sequences of samples from thousands of years ago have been reconstructed. For example from Neanderthals it was fairly recently announced. But when you read of such tours de force remember that the sequences are mitochondrial DNA, that is non-nuclear DNA which is several orders of magnitude more abundant (by molarity) than nuclear DNA. Which is fine if your purpose is to say something of evolutionary relationships, e.g. the relationship of Neanderthals with present human population. It will in any case always be related - for great part identical - to a known DNA and you know what you are looking for.

For mammoths getting the material is fairly favourable. The elephant genome is fairly completely known and checking now I am amazed to discover that so is the mammoth! http://www.nature.com/nature/journal/v456/n7220/full/456330a.html The power of present techniques is fantastic. The implantation of a fertilised mammoth egg in an elephant I would guess could work - they are closely related. As experimental sciences go it is not for the impatient since an elephant has a 3-yr gestation. But knowing the DNA sequence is not the same thing as having a mammoth cell. I doubt they have got any mammoth cells they could resuscitate. Barring future breakthroughs I guess they would substitute the relatively few genes that are different in the two species. But that is still a lot of genes. So probably they wouldn't change all of them but just some crucial ones, to get something that wasn't a mammoth that could be related to any mammoth that ever lived but something that looks and functions quite like one. They won't know which of all the genes the crucial ones are though they might work out some that are important.

It would need quite a lot of determination or else further breakthroughs; I wouldn't bet you will see it in your lifetime but you may just see it for some easier species.

 

[Evo]

I've once read an article about a team of scientists who were about to (or wanted to) clone a mammoth with the aid of using elephants.
I have two questions on this topic:
1. Is that possible? (I assume they're using a recovered mammoth genome and in vitro fertilization)
2. If it's possible, how about cloning e.g. a homo erectus?

I think the first mistake to clear up here is that stoneage man, includes modern man. Homo Sapiens go back 200k years, up to 41K years ago.

http://en.wikipedia.org/wiki/Timeline_of_human_prehistory#Middle_Paleolithic


Homo erectus lived 1.8 to 1.2 million years ago, not even close, They were not stone age.

http://en.wikipedia.org/wiki/Timeline_of_human_prehistory

 

[CCWilson]

Let's say that scientists were able, by analyzing fragments from many different specimens, to work out the genome of a prehistoric beast, or a dinosaur, or even a homo erectus or Neanderthal. Or to make it easier, let's say that we have the genome of a current human or a worm. Will it ever be practical to plug that data into a machine and have it produce an actual full DNA sequence, which could then be implanted into an ovum, which could be stimulated to divide and create, a la Jurassic Park, said dinosaur or Neanderthal or earthworm or Sarah Palin?

 

[Ygggdrasil]

Let's break the question up into two parts:

Will it ever be practical to plug that data into a machine and have it produce an actual full DNA sequence

This has been done for viruses (http://dx.doi.org/10.1126/science.1072266) and bacteria (http://dx.doi.org/10.1126/science.1151721), but not any organisms with a larger genomes. Assembling an ~1 million base pair genome was estimated to cost ~$40 million, so constructing the full 3 trillion base pairs of the human genome would be extremely costly. It may be possible to engineer the genome of interest by introducing changes into an existing genome (for an example of this approach applied to bacteria see, http://dx.doi.org/10.1126/science.1205822), but this approach would also be very costly. The costs for either approach, however, might be expected to decrease over time. Furthermore, we lack good means of assembling and manipulating DNA molecules the size of human chromosomes, so some work would need to be done in this area.

which could then be implanted into an ovum, which could be stimulated to divide and create, a la Jurassic Park, said dinosaur or Neanderthal or earthworm or Sarah Palin?

This has been achieved for bacteria (http://dx.doi.org/10.1126/science.1190719), but I forsee significant obstacles in its application to more complex organisms. Unlike in bacteria, eukaryotic cells rely on many epigenetic modifications to the genome that we do not fully understand and are absent from chemically synthesized DNA. While it has been shown that these epigenetic modifications can be altered to reprogram cells into different lineages(http://dx.doi.org/10.1016/j.cell.2006.07.024 ), it is still uncertain whether similar techniques could be developed to allow synthetic DNA from one organism to function correctly in the ovum of a related species.

 

[CCWilson]

Very interesting. You'd have to assume that 100 years from now such an assembly machine might be practical and cost-effective. With regard to epigenetics - do we know whether they are essential to the development of a functioning individual, or simply improvements? In other words, could naked DNA produce a living organism? I'd expect so, since epigenetic changes don't last all that many generations, I thought.

 

[Ygggdrasil]

Sure. In fact, it would not surprise me if in 10-20 years, the synthesis and assembly of a full human genome is practical.

In terms of epigenetics, both a skin cell and an embryonic stem cell have the same DNA sequence yet only the embryonic stem cell is capable of producing a living organism. Therefore, epigenetic regulation of DNA plays very important roles in determining whether a particular cell can develop into a full organism.