In the first part, I have reported short-Oedipus, Following a spell of his own mother to wife and children took the father to her. The right to existing moral condemnation of inbreeding in human society also influences our view of inbreeding in animal breeding. So wrote Hans Zurhöfer example (an outstanding pigeon breeders in the 50s-70s and founder of Total widowhood) in his books, full of indignation against inbreeding in pigeons, since it is unnatural and could only be the result of decay. But how is the inbreeding from the perspective of Polpulationsgenetik assessed?
inbreeding, what happened in detail?
speak of inbreeding, we strictly in population genetics whenever father and mother have common ancestors. The closer the two animals are relative, the greater the inbreeding. By inbreeding of paternal and maternal genetic material with the same part is introduced. This means that meet the juvenile at these sites in the genome like alleles of the genes, ie the number of homozygous gene pairs is increased. This homozyoten gene pairs has the effect that the direct descendants of this animal saved always get such a homozygous allele occurring inherited. That is, the higher the homozygosity of the genome of an animal, the more sure you can predict which genes the children will receive. But a note at this point very important, it still says nothing about whether these genes are "good" or "bad" genes!
The inbreeding coefficient, an important characteristic
As for "close relatives" means can be calculated in practice. For example, if a daughter is mated to her father, the young animals are even half of the genes from the father and the prisoners of the genes from the mother. But half of the maternal genes are genes already been derived from the father. If each of these genes represent a random selection of the paternal genome, it is assumed that 25% of the genes present the young animal homozygous, because here each Genes of the father, and genes of the father over the mother have taken Coming (50% father genes have a probability of 50% to another Vatergen take is 25% of gene pairs with the same alleles).
generation Pro / birth, which is between the same relative, reduced the take probably the same genes, by a factor of two (because of the cleavage of the 40 pairs of chromosomes into two groups each with 40 single strands during meiosis). Thus, therefore, would be likely to present genes in homozygous father x-grandchild pairs, only 12.5% and half-siblings also pairs 12.5% (three births). But
increases the probability of homozygous genes available with each course to have common ancestors, and these probabilities are simply added together. Thus, the expected homozygosity is a full-sib mating again at 25% (two common ancestors and three births). because of this common ancestor and random Genverteilung expected homozygosity in the genome of the young animal is called the inbreeding coefficient . The actual calculation formula can google it easily leads at this point too far.
The calculation by hand is a bit tedious especially for many generations. Against this background, it is incomprehensible to me until today, why not one on the market "pigeon breeding" program the automatic calculation of the inbreeding coefficient supported. Pretty much any breeding program for rabbits, dogs, chickens and horses, this can! "Pigeon breeding" programs seem unfortunately to express beautiful trees meant to be. A free tool (because it is a stripped down version of professional tools) can be found here: www.tenset.co.uk/fspeed/
the program with a table, we "fed" in which each row the number of the animal, the father and mother separated by commas are written.
The inbreeding coefficient of the example of "Jonge Merckx"
The "Jonge Merckx is "one of the most important pigeons, the Janssen brothers have grown, because not only does he flew 15 times 1st prize, virtually all are good sires and Zuchtauben the recent past of the Janssen brothers from him. Examples of what I call only three of his grandchildren: "Blue Winter Jonge" (father of "Klamper" and "Vechter (alloying) and Grandpa" Lowieke (vdPasch)), "Afgekeurde" and "rockets" (critical strain dove for the blow G. & C to. Koopman). As far as the family relations were documented, I have tried the course of inbreeding coefficient in the pedigree of "Jonge Merckx" calculate.
Since I have the exact relationships to the Janssen Pigeons before 1950 could not figure out completely, the Janssen brothers but have previously operated Verwandschaftzzucht is of generally higher inbreeding coefficient than the stated assumed, however, one can show well in this example, a few things.
By a click on the picture is the lineage it enlarged.
The "Jonge Merckx" had to say after my research, at least one inbreeding coefficient (abbreviated pedigree IZK) of 45%. This means 45% of its genetic material were probably from homozygous, was thus secured transferred to its offspring. It is no coincidence that He was known as a more lasting sire.
45% is an extremely high value, because this is almost twice as high as the inbreeding coefficient of a daughter x father product! One can also see how the inbred from generation to generation increased steadily as more and more equal relationship occurred in the family tree (part of the family tree, is beyond the 5th generation not shown). is also apparent that for the consideration of inbreeding within a breeding strategy is very much important to know a family tree as completely and as far back as possible leader.
the repeatedly expressed view that trees in the breeding plan are important, because they are "no fly" can be dangerous because you might lose sight of the important relationship links, and thus, for example in breeding pairs, without that you are aware, because the same relatives already be older. It would have the pairing of the parents of the "Small ads of 65" not recognized as a breeding relationship, although with her already inbreeding coefficient of 9.4% is present (ie more than a father x grandson mating).
has, however, the "Jonge Merckx" itself never directly produced an outstandingly good flying juvenile, were found more successes in the following generations, and they were usually celebrated with other breeders. And in any case were the travel services of the Janssen brothers from that date in the 70's, downhill! What had happened? Finally, had the "Jonge Merckx" but obviously a big package of "good" genes, which he passed on to his offspring. Why then were the successes in the Janssens getting worse?
inbreeding depression and heterosis
The concentration of genes by inbreeding concentrates the genes of a common ancestor in a random composition and not only the "good" genes . If a common relative of a rare recessive gene as a specific disease susceptibility has, then is not this gene in pairs with related animals probably never negative impact because it is the only stock in the pigeon with this gene. But then his offspring were mated in breeding, so this gene may occur suddenly homozygous, and thus phenotypically visible. Say morbidity would occur with this breed animal.
By inbreeding so connect recessive rare qualities to light, and some of them can have a negative effect on the phenotype. It is clear that the higher the homozygosity, the higher is the probability that such negative effects come to light.
influence Furthermore, different genes, too each other (epistasis or also called overdominance). The more homozygosity in the genome is available, the more likely are epistatic interactions. And again: some thereof have a negative effect on the phenotype.
The more the inbreeding that is, the higher the probability that negative so far hidden in the genetic material properties are visible. This effect is called commonly by inbreeding depression.
Another effect of inbreeding is that the genetic variation decreases the inbred animals in the extent to which decreases the number of different ancestors. This may have the positive effect that one has the genetic material present very good animals less concentrated. But this can also have the negative effect that decreases the adaptability of these animals to changing environmental conditions. For an allele that has been "bred out" is irretrievably lost.
The extremely high degree of inbreeding of the "Jonge Merckx" shows how well its sophisticated must the original material of Janssens once have been, with which they began their breeding. For there to be found in the literature that shows inbreeding depression often even with an inbreeding coefficient of 10% negative impact. But the "Jonge Merckx", despite the value of 45% with 15 1.Konkursen in flying an exception dove. For him, apparently mainly "good" genes were concentrated benefits. In also shows the high value of the "Jonge Merckx" but also that he possessed only a much smaller sized gent variation, other than the pigeon breeders. For the Janssens even he could again be paired with him related animals only, so that genetic depletion and inbreeding its pure Janssen-children increased even more. Changing requirements (eg new pathogens) and increasing inbreeding depression paved the success of the Janssens to a foreseeable end.
high unabated until the 90s, but the quality of Janssen-pigeons as a sire of top prices (especially on short and medium range). They showed this ability in particular when they were not completely crossed with related animals of another breeder. And it quickly becomes clear why: In one stroke (ie in the first mating), the high homozygosity, which is mainly responsible for the problems is reduced to an inbreeding coefficient of 0%. The negative consequences of inbreeding are so strong also disappeared in a flash. But in return, the children receive a great package from the "good" genes of the "Jonge Merckx", acting through their additive gene effect continues.
This sudden improvement in his performance of the phenotype in young animals an intersection pairing is called heterosis. She is so to speak, the counterpart to inbreeding depression .
0 comments:
Post a Comment