Inbreeding

Today's topic: Inbreeding. What is inbreeding and which problems brings with it?

For sure we all have heard about inbreeding. When we hear about the Amish, about some royal families or even in some historical games (Crusader Kings I and II), inbreeding is almost always present. It means marriage, union or reproduction between individuals of common ancestry, ie. of the same family or lineage.

Picture from xenohistorian.faithweb.com

Also, inbreeding usually represents something bad. Some traits come with it, such as reduced fertility, facial asymmetry, lower birth rate or increased genetic disorders (albinism, hexadactilia, etc.). But, genetically, why is inbreeding so deleterious?

Let me tell you about the genes. We have a pair of each chromosome, in total 22 (plus XX or XY), and consequently a pair of each gene -one per chromosome-. We inherit one from the father and one from the mother. The expression of a gene depends on the pattern of expression, I mean, if one allele -alternative form of the same gene- is dominant will need just one dominant of those two for produce a phenotype; but if it is recessive it will need both. The same with a mutation in a gene.

Picture from xenohistorian.faithweb.com

And what happen if you cross the same alleles of a normal or mutated gene every generation? Correct! We finally, by chance, arrive to a stable population with homozygosity for the majority of the genes. What means that all the small diseases and deleterious traits that were hidden under the recessive pattern arise.

For a long, long time, it has been thought that inbreeding of families among them, or among only one or two another, could create individuals with their best qualities -that was the ruin of Darwin's family-. One could think that, why, if some mutations are recessive, could not we inherit superpower traits instead of diseases?

For answering this question, I strongly recommend that we all remind how complex we human beings are and what is more probable if we change something of our gear: improvement, permanence or deterioration.

We will talk about the theories of how could we solve inbreeding in nature, about Darwin's family, as well as about albinism and other genetic diseases very soon!