Female mammals can't make babies on their own. For the foreseeable future, this won't be changing either.
The reason mammals can't do this has to do with something called genetic imprinting. The DNA we inherit from our moms is very similar to what we get from our dads. But there are differences.
Scientists found these differences by studying sperm and egg DNA. They discovered that some part of the DNA is changed in certain places in the sperm and other places in the egg.
It is these differences that make fertilization necessary. A fertilized egg needs both sets of differences in order to grow.
So if you just double the DNA of an egg, you won't get both sets of differences. And the new egg won't grow into an adult.
But it will make it partway. In fact, far enough long to make embryonic stem cells.
Embryonic stem cells hold a great deal of promise (click here
to learn more). A big problem, though, is that a patient will reject someone else's stem cells. So scientists are trying to make embryonic stem cells from adults.
One way to do this is to clone the adult. This has obvious ethical problems, some of which are being dealt with (click here
to learn more).
Another way is to make a female's egg start to grow on its own. The first step is to get it to double its chromosome number. There are a variety of ways to do this.
The next step is to grow it a bit and collect some embryonic stem cells. They have done this and are beginning to study in detail what can be done with these cells.
It is important to note, though, that these stem cells are not from a clone. The DNA is different from mom's.
Remember, an egg has only half of the mom's DNA. When the egg isn't fertilized, the DNA in the egg is doubled. In essence, half of mom's DNA has been duplicated.
So the new cell has twice as much of half of mom's DNA. Simple, huh?
Let's give a concrete example. Imagine that mom is a carrier for red hair (click here
to learn more about red hair). This means that one of her MC1R genes causes red hair and the other doesn't. Mom doesn't have red hair but carries the gene.
Each egg has a 50-50 shot of getting the red hair gene. Let's say the one chosen to make the stem cells is the one that has the red hair gene.
When the gene is duplicated, the new stem cell would have two red hair genes. If it had hair, it would have red hair. Which is different from mom.
But the cells would still be similar enough not to be rejected by the patient. This is why scientists are trying to create these cells.
Of course this process will only work for women. But perhaps one day the process could be repeated with sperm DNA put into an egg without chromosomes. Then both women and men could have personalized embryonic stem cells.
Parthenogenesis is not only cool, but it might help us solve the problem of embryonic stem cells. Thanks Komodos for showing us another way to get these cells!