During the Torchwood: Miracle Day second episode, one of the experiments that doctors are doing to investigate the lack of death is to monitor some cells. They examine the length of the telomeres, which are a way to track aging, as they shorten as you get older. My question is related to the science here. They measure the telomeres once a day for two days, and from that are able to measure a difference in their length. Is that remotely possible to detect telomere shortening over such a small period of time, or is this a case of bad science in fiction?
The answer is realistically no. It is true that each time the DNA of a cell replicates that the telomeres shorten just a little bit, but there are mechanisms in place that cells use to lengthen these telomeres and counteract the shortening effect.
The average human cell divides every 10 hours, so say 5 times in 2 days. Each replication shortens the telomeres by 4 bases. That's ~20 bases in 2 days. Given that DNA is billions of bases long, that's a rather small %. Taking into account that there is variation in telomere length between any two people, any two of their cells, and any of their chromosomes, the fact that there are 23 chromosomes, and that they are being lengthened at the same time as well, it is unlikely that with all this variation one would be able to tell how much shorter the cell gets, but like anything under the right circumstances it could be possible. If you made sure it was a single chromosome and you managed to look at each chromosome individually and a ton of other things then I guess you could.
Also, it would take some time (at least a week or so) to figure out the exact length of telomeres in order to be precise enough to keep the error in the results to under 5% (generally the standard to know your results are valid).