I saw that Clove already has a question about DNA, but this one is a bit different so I started a new thread rather than confuse his one. Sorry if it seems too similar.

This one is for all you science buffs:

In the near future, there is a scanning technology used to identify people. It works by taking a minute sample of your DNA and analysing it to see who you are. In this way, you can pay for things without the need for carrying a credit card around and suchlike.

However, there is some kind of a disaster occuring that is going to destroy the world & the only way to prevent it from happening is to send people back in time.

Now then, the mechanism for time travel relies on the DNA of individuals having a certain very rare structure. So all the scanning machines in the world have been programmed to identify this rarity when they scan people. Hence my character is dragged out of his normal environment and sent begrudgingly through space and time to save the day.

So, I guess my questions are:

1) Is the use of DNA to identify individuals theoretically possible?

2) Anyone know of any rare DNA sequences that would only appear in say 6 people in the whole world?

Nuclear DNA is extremely discriminating and can place a person at the scene of the crime and identify them with 99% accuracy; however, the problem arises when an identical twin or subsequent sibling sharing the exact same egg and sperm is concerned. Identical twins have the same DNA pattern and the DNA will not differentiate between the two. In order for detectives to determine which twin, triplet etc pulled the trigger, we need fingerprints.

Patterns, such as the familiar patch work quilt patterns on Calico cats, stripes on tigers and Zebras and fingerprints on humans are not replicated in DNA.

Peace,
Scott

The guy isn't special. He's just an everyday Jo Shmo.

It's just that there's this need to send people back in time so that they can resolve the disaster. However, the catch is that the machine that can send people back in time, will destroy anyone apart from those with this particular DNA configuration. So the people best skilled, trained or knowledgable dont get to go. They have to send in random people who just happen to have the correct make up.

AAA, ACT, TUT...

just make up something like

Also look to Richard K. Morgan's Takeshi Kovach books for DNA stuff. But again this is "hard" sci-fi but he uses it well.

Note: to me "hard" sci-fi gives the scientific foundation for a technology in use rather than simply saying

Character X licked his thumb and dna from his silva let the computer identitfy him (very rough paraphrase from Altered Carbon by Richard K. Morgan)

or

Character Y has a genetic mutation that lets him move through time. Its uncontrollable and sometimes dangerous since he can't take anything on these trips ie he arrives somewhen naked as a jay bird (very rough sketch of Time Traveller's Wife by Audrey Niffenneger)

This in comparison to A "hard" sci-fi author tries to give me the physics/biology of the event.

For me as a reader, I don't think I would need to hear what chromosome, what disease, or what anything else they're talking about. It's just something specific about his DNA that makes him a candidate by random chance.

If they can create a time-travel device in the first place, how come they can't decide who it transfers?

Now, something that would work for me is that the device pick up a random six people off of the face of the earth.

But I don't know if that helps further your plot at all.

Is the genetic strain limited to a single racial group?

Perhaps all the timetraveller DO get murdered with a disease like this. Maybe genetic scientists are breeding new timetravellers but it will take 20 years for the subjects to get to maturity. In the interim your MC with the right genetic strain may be discovered living in a commune of hippy drop-outs who deliberately fly under the genetic radar. Not only can he save the day but he has a built-in job when he gets back, training up the time-travelling kids and maybe he is subversive enough to imbue them with his own brand of pseudo-hippy rebel ideas

Think about the soviet attempts to homogenise the crops grown by their peasants. There were bands of agricultural rebels in the hills of Tajikistan etc, who resited the idea and hid up traditional crop seeds against a time when they could grow them again.

Now that the soviet regime has come to an end, the rebel farmers are growing their traditional varieties again. Western scientists are going into these remote communities and bioprospecting -- seeking out genes that will strengthen the food crops of the west.

Recently I asked a similar question about time travel and was told to be careful of the grandfather paradox. I ditto that to you.

Also, I'm not so sure about the grandfather / son parodox. This guy is gonna find out he's going back to kill another version of himself that was sent back in time the first time around, but was sent with the wrong message.

See...seeing as there's only a very rare number of people with the syndrome. Only he can go back and do it. Argghhh.

Lol...Perhaps not though.
My main objective for setting this up is so that I have a reason for the people to be isolated together & throw some mysterious goings on at them at the same time.

You need to creativly avoid the paradox.

so he got sent back in 2004 to kill the self that went back in 2005? wont work because the 2005 self would have the 2004 memory.

Unless, he has the memory and the 2005 self learns something and goes back anyway, knowing that if his memories serve correctly he killed the 2005 self(him now) but he has to change that somehow to save the world.

A brilliant physics professor annnounces a major breakthrough and says he'll describe it to everyone tomorrow. The next day he announces he's discovered how to time travel. Later that day he's teaching a class and everyone on campus crowds into hear him hoping he'll give them the full story when suddenly a man walk into the room and rushes at him with a knife but right as the knife was to cut him the man and knife dissappear. Needless to say this causes quite a stir and all the newspapers cover it. the next day he's teaching a different class and a man almost exactly like the first comes into the room pulls a gun and fires but the professor isn't hurt and the man gun and bullet are all gone.

So the next day CNN shows up on campus to see if the mysterious assassin tries again.

The entire class session goes smoothly and when the professor leaves the CNN reporter asks him "Professor Why do you think the assassin didn't come today?"

The professor replied "I decieded to never have children."

Paradox isn't a problem if you're planning to actually change the past (or prevent it from being changed). If it's possible in the first place, then self consistency isn't required.

For your science, take the mushroom approach. None of your main characters really understands why it works. At a guess, I'd venture that the qualifying characteristic is that you're genetically identical to a physically similar person living in the target time period (get this, perhaps only the mind of the traveler is sent back, like in Clap Hands and Sing). So almost anyone could go back in time a few months or years, but they need to send someone back to whenever.

Or perhaps the time travel process requires the subject to be chemically prepped somehow, and they've established that, between a certain combinations of genetic resistances common to these people, they might survive being injected with the chemicals that are needed to port someone through.

My initial idea was that the genetic requirement was consistency based, but if you're going to be changing the past anyway, causality violation isn't a problem.