Chromosome Genetics

Knowledge abounds here on Earth about the number of chromosomes humans have and how gender is determined by whether a fertilized egg cell has an XY or XX chromosome pair. It's less well known that cell division includes the opening up of all nuclear DNA pairs and the splitting of them into two batches before replication. Even less well known is how hard it is, given today's technology, to separate chromosomes so they can be accessed individually.

It is not exactly clear if there is any other way of harnessing the protein synthesis control capabilities of DNA so that alien cells might have a different way of doing it. Nor even is it known if there are alternatives to DNA to carry genetic information. Genetics in this area is like exo-planetary studies before any exo-planets were discovered. Everything is speculation.

These two questions are somewhat independent. If an alien planet had non-DNA genomes, that still does not mean that they would not have all the genetic information divided up into chromosomes. The alternatives are to have more than one nucleus in the cell, with perhaps one chromosome in each, or to have one nucleus with only one chromosome pair having all the DNA or its equivalent. Why did Earth evolve multiple chromosomes, or rather, why don't all species have just one large circular chromosome as do many single-celled organisms? What is the evolutionary advantage and would it be universal, meaning on other planets as well?

Among contemporary bacteria, there are some with one, two or more circular chromosomes, some with linear chromosomes, and some with a combination. After billions of years of evolution, the competition for a chromosomal shape has not been won by any arrangement, so for bacteria and other prokaryotes at least, there must be little evolutionary advantage between them. This is not true for eukaryotes, multi-cellular organisms, which all seem to have linear chromosomes. Most eukaryotes also have some legacy circular chromosome material, located in the mitochondria or elsewhere, which reproduce independently of the nuclear DNA during cell division.

One advantage is obvious. To have genetic information for many different types of cells, as well as the signaling information for organizing them, there must be much more information, and a circular chromosome or a single linear chromosome with all this information would simply be too large to fit into the nucleus, or for the meiotic proteins to handle. Having everything in large numbers of diverse mitochondria also seems evolutionarily difficult, for the organization of cell replication. So, using DNA or anything else, it appears likely that alien species will have multiple linear chromosomes.

Alien geneticists may run into the same problem that Earth geneticists have: separating chromosomes is difficult. The processes within the cell are quite complex, and there is not enough information on them to allow them to be replicated or imitated in a genetics lab. Neither have there been any simple mechanical solutions to separating chromosomes. Perhaps we are missing the right discovery. By the time asymptotic technology arrives in the genetics area, however, this problem will have been solved.

It's not clear that the ordering of advances and inventions in the genetics grand transformation will make much difference in how an alien civilization will develop. The end result would be the same. But chromosome separation would allow some cost-savings in making genetic changes to organisms, or to the creation of synthetic organisms. If this cost-savings is large, it would emphasize the possibility of having genetically modified or created organisms throughout the civilization.

All we can do now is map the genome of humans and other organisms, and use that information for diagnoses, or in plant and animal breeding. There is some work being done on inserting novel genes into existing plant and animal genomes, but it is very slow. If it were possible to isolate chromosomes rapidly and inexpensively, this would speed up the process. It would also make the process of genetic modification more certain, as a laboratory could simply work with one chromosome and modify it, without having to worry if the modification methodology would accidentally make a modification in another chromosome, with a similar stretch of DNA.

One interesting question to ask is how would an advanced alien society prepare the genetics of their successive generations of their population. Suppose there is an inexpensive way to separate chromosomes. Then, the alien society could simply decide to choose the best set of chromosomes from the copies available. If there is some optimal set, then all the aliens in later generations would be like clones. Alternatively, if the selection was out of the set of a pair of parents (assuming two genders), a wide variety of individuals would remain, but there would be a trend toward more healthy individuals with better capabilities.

Similarly, if there were pairs of parents with some genetic deficiency in one chromosome, specifically in one of the parents, then that chromosome could be eliminated in the resulting next-generation individual. This would result in the gradual elimination of genetic diseases and other problems, although errors in replication remain possible and there would always be a risk of some new mutation arising.

There are many syndromes which arise because of the improper copying of whole chromosomes, meaning extra copies, and with chromosome separation technology, these would be reduced or eliminated as well. Broken chromosomes could be sorted out as well, and mutations arising from copying errors would be detectable and removable. Reading the genome would be less computationally intensive and less prone to mistakes, if each chromosome was read individually. The current Earth method of batching all the chromosomes together and then sorting them out after all the fragments have been read is clearly something that can be improved on.

The technology to separate chromosomes does not seem to be on the horizon, meaning the old methods would be used here for a decade or so. Microbiological investigation into how to make a cell nucleus separate and then how to create microtubules to reach into the mixture and connect to individual chromosomes needs to be done. Once it is well understood how nature accomplishes this task, it would be more reasonable to expect that genetics laboratories can come up with some combination of biological and physical equipment to accomplish chromosome separation. After this, we might see genetics jump forward very fast in potential applications, and this will give us a much clearer idea of what an advanced alien society might be doing with their own technology in this area.