I was taking a Biology class today about cloning and DNA. My professor explained that if you made a clone of yourself, it would still be “your DNA age.”
So my question is: why does DNA age?
Will it be possible for humanity to discover a way to make clones that are born with new DNA?
In: Biology
Imagine your DNA as a really long, multicolored piece of string. It’s colored with four different colors in blocks of different sizes, and all three of the orders, colors, and sizes of each section are important.
Your body needs to make copies of your DNA constantly. Think of this like grabbing two pieces of the string between your finger and thumb of each hand, then stretching out the middle bit. You can copy that middle piece just by putting all the right colored sections together. You can’t make a copy of the bits your fingers are covering up, since you can’t see it, but that’s fine; you usually only need a little bit at a time anyway.
But what if you need to copy the *whole* string? You have to do it all at once, since your cells don’t really have “memory”; if you try to do it in pieces, your body won’t know how to put them together. So the only way to do it is to grab both ends of the string and copy everything in the middle. This means you lose a bit of the string at each end every time you make a complete copy.
Now, your DNA is built to accommodate this. At each end is a chunk of “junk” data, like a piece of the string that’s all one repeating pattern that you don’t really care about. You can lose some of that and it won’t affect the rest of the string. But those end sections – called telomeres – can only be so long. Eventually, that process of copying the middle and losing some of the ends runs out of “junk” and has to start cutting off actual, useful sections. That’s when aging becomes a problem.
(Of course, the real process is slightly more complicated than this. DNA is a double-helix, meaning it’s two strings, and you can only copy it by making a new string with exactly the *opposite* colors in each section. Making a complete, identical copy actually means copying one section once in negative, then building the matching half from that, so you’re basically copying it twice every time.)
As for clones, it’s a persistent myth that clones of adult animals age more quickly. This stems from Dolly the sheep, the first clone of an adult mammal. Dolly was cloned from a six-year-old adult, half the maximum age for that type of sheep (about eleven or twelve years). Dolly died at the age of six-and-a-half, leading to popular speculation that she had been born with a “genetic age” of six years.
But Dolly didn’t die of old age, and in fact she showed no symptoms associated with advanced age for a sheep. She died of a lung infection and arthritis, likely a result of being kept in captivity as a research subject for her entire life. Sheep who spend a lot of time indoors are prone to developing respiratory illnesses, and the same illness killed other, non-clone sheep in Dolly’s flock.
As for why cloning doesn’t fall into the same genetic aging problems as normal cell replication, the reason is the same reason we aren’t *all* born with the same genetic age as our parents. When an egg begins developing into an embryo, all the cells are put into a special state that lets them *rebuild* their telomeres. This is good news for an embryo, which has to start from a single cell and build into an entire body by repeatedly doubling itself; if telomeres shortened every time, we’d die of old age before we could even be born.
But this process switches off later in life when we don’t need to make cells so quickly. This is actually a good thing, as we don’t want cells to replicate endlessly; endless cell replication is what cancer is, after all. But it does mean that we eventually succumb to old age.
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