Expert: Dana Krempels, Ph.D. - 9/7/2009

Question

 Hello Danna. I had a look at you description and it looks like you will certainly be able to help with my questions. My questions are quite basic in terms of its topic, which is about cloning. I would like to ask you a few specific but conventional questions on the topic of cloning. I have 10 short and pretty general questions in this topic and I am assuming you won’t need to explain the answers in much detail for these questions.  But please feel free to leave any question if it seems too difficult for you to provide an answer to. So here goes, first of all does cloning require DNA or samples from both male and female or is it possible to compromise without either for e.g.- if researchers found a DNA sample of a male dinosaur, could they possible clone it without the female sample? Is it even feasible to consider cloning a dinosaur even if they found a DNA sample from such long ago?  How intricate or difficult is it to clone using the DNA? Sorry if I sound a bit naïve but is it also plausible to clone using sperms or is that the same as using DNA samples? Has all or most variety of different species of animals and even fowls been tested for cloning such as bats, lizards, birds, snakes, lion, deer, etc.? Also,  is cloning humans a much more complex and perhaps tedious process compared to animals? What amount of DNA sample would one require in order to clone or does the size of the sample not matter as long as a DNA is extracted from the sample? We are aware that consecutive hybrids has not come to pass yet but cloning or breeding with species with similar aspects could be feasible. So the question is that would it be plausible to clone two species such as a sheep and a horse or chicken and an eagle, etc.? Subsequently there are 2 last short question left. Would it be adequate or consecutive to use 3 DNA or sperm samples instead of two like an odd number for e.g.- 2 male and 1 female, could such a cloning be a success? And lastly what is required in an experiment in the place of a female womb, is it some kind of artificial nutritional bladder? So these are all the questions I have to find the answers to in order to understand the general concept of cloning. And if you would help me conceive it, I shall be very much thankful for your effort. Your help will be much appreciated. Thank you.  

Answer
Dear Derick,

In answer to your questions:

1.  does cloning require DNA or samples from both male and female or is it possible to compromise without either

Cloning is a form of asexual reproduction, so all you need is a single cell (or cell nucleus) from a single donor animal--male or female--to make a clone.  That is, if you have all the proper equipment are are successful (which not every cloning attempt is!)

2. Is it even feasible to consider cloning a dinosaur even if they found a DNA sample from such long ago?

It would depend on how complete the sample of DNA is. If you have an entire cell's worth, with all genes intact, then it would be possible.  But any missing information makes the process that much more difficult, since a lot of reconstruction of the genome (if this were possible) would be guesswork. (This is why Michael Crichton had the idea of "filling in" missing dinosaur genes with frog genes.  Okay, so he was a pre-med and didn't really do his genetics homework....)

3.  How intricate or difficult is it to clone using the DNA?

It's incredibly difficult, and the difficulty varies by species.  For every cloning attempt that's successful, hundreds or thousands may have been tried.

4.  Is it also plausible to clone using sperms or is that the same as using DNA samples

Most living organisms are diploid. This means that they have two entire copies of the genome: one from mom, and one from dad.  Two copies of every gene are ordinarily required for normal growth and development.  Thus, it would not likely be possible to clone an entire organism from a single sperm cell, since its nucleus contains only *one* copy of the genome (dad's), not two.  Add to this the problem that if the sperm carries a Y chromosome instead of an X (it has to carry one or the other of the two different types of sex chromosomes), you could not clone it, even if you doubled its genome.  The information on the Y chromosome alone is insufficient for normal embryo development.  You'd have to introduce an X chromosome to get things to have a chance of working.

You might be able to clone from a single ovum, if you could double the genome without the nucleus dividing, thus making it diploid again.  But the problem here would be identical genomes, and that creates all sorts of potential problems.

5.  Has all or most variety of different species of animals and even fowls been tested for cloning such as bats, lizards, birds, snakes, lion, deer, etc.?

The genomes of all species have not yet been sequenced, so most species of living organisms have not yet been considered for cloning.

6.  Is cloning humans a much more complex and perhaps tedious process compared to animals?

Although researchers are certainly interested in knowing whether humans can be cloned, it appears that primates, in general, present greater obstacles to cloning than certain other species. This has to do with their different developmental critical periods at the one-cell, fertilized egg (zygote) stage, as well as other unique problems.  Humans *are* animals, but they belong to a group of animals that is particularly challenging to current cloning techniques.

7.  What amount of DNA sample would one require in order to clone or does the size of the sample not matter as long as a DNA is extracted from the sample?

The smallest amount you'd need would be the complete genetic components of a single, diploid cell.  It's possible that one could try to clone a diploid cell from a gamete by doubling the genome.  But again, if both genomes are identical, there will be problems from homozygosity at all the gene loci (if there are harmful, recessive mutant genes in the genome, these will be expressed because they don't have a different version of the gene to "mask" the harmful trait).

8.  Would it be plausible to clone two species such as a sheep and a horse or chicken and an eagle,

What you're describing is known as a chimera:  an organism containing genes from two or more different species.  These exist now, but mostly in bacteria and mice and other lab animals.  Nothing so spectacular as a hybrid sheep/horse or chicken/eagle.  

The chimeras of today are things like zebra fish (or even mice and rabbits) that express an inserted gene from a jellyfish that makes them glow in the dark.  Or a bacterium that can produce insulin because it has been inoculated with the human insulin gene.  

But who knows in the future?  Right now, it's science fiction.  But the more we know about the genome, the more these things have a chance to become reality.  (Whether this is a good thing or not is a matter of opinion.)

9.  Would it be adequate or consecutive to use 3 DNA or sperm samples instead of two like an odd number for e.g.- 2 male and 1 female, could such a cloning be a success?

Although many plants can survive (and even thrive) with more than two copies of the genome, animals generally do not develop normally with either one or three copies.  Almost all animals are diploid (two copies of the genome), so it would be difficult to overcome that developmental barrier and create an organism with three copies of the genome.

10.  What is required in an experiment in the place of a female womb, is it some kind of artificial nutritional bladder?

The requirements for embryo development depend on the species.  If you're growing a fish clone, all you need is the right kind of aqueous environment.  For terrestrial animals that develop in an egg, you'd have to mimic the conditions in an egg.  And for a mammal, you'd have to mimic the conditions (including nutrient transfer) in the uterus.  That can be incredibly complex, and will vary with species.

I know some of this might not be clear if you don't have a background in genetics, but I hope some of this helps. If something isn't clear, please ask.

Dana