Inheritance
Percentages of Inheritance
According to standard genetic views the approximate percentage of blood influence for ancestors in each generation is:
Parents contribute 50%
Grandparents 25%
3rd Generation 12.5%
4th generation 6.25%
5th generation 3.125%
6th generation 1.5625%
So, a foal will inherit 50% of its genes from each parent - but we cannot tell which 50% this will be.
These fixed percentages in real life are in fact only an estimate.
Due to recombination, genetic variation and mutations, genes from an ancestor do not always pass on perfectly as these percentages indicate - or act in ways they should - and they can change places on the chromosome
For instance, one grandparent may contribute more chromosomes than another.
With grandparents it can look more like this
Grandparent 1 - 3.4%
Grandparent 2 - 1.5%
Grandparent 3 - 1.6%
Grandparent 4 - 3%
There are 64 ancestors at the 6th generation and due to recombination, it is entirely possible that some did not contribute any genes to the foal at all - or may have contributed a whole lot more than they would be thought to according to their pedigree position and to standard figures.
This is where full siblings come in again – if a mating has been successful in producing a top horse and it is repeated - it is virtually impossible that the same genes will be present in the sibling. On average siblings share only 50% of their genetic material and half siblings about 25% shared DNA.
Of course, there are cases of full siblings that have both competed to the top level in sport
Examples
Isabell Werths GP horse Salinero is a full brother to the 1.60m champion jumper Seven Up
In general the dangers of buying a sibling to a champion for performance in top sport is a big risk - and many people have lost money doing this - it is usually safer if the sibling is the same sex.
For breeding purposes, buying a sibling to a champion performer has a higher probability of breeding another champion - if both are from a top mare line that is known for producing horses that perform at the top of the sport
Of course, if you have a beautifully balanced genetically compatible mating on paper - and have well researched other factors such as conformation ,performance and temperament - this will also increase the probability factors of siblings both being good horses.
It is recommended that you repeat the mating a few times as the first foal may not be the best one - remembering that there are 4 possible genetic combinations for each sex that can arise at meiosis.
Another way to try to ensure that the foal inherits the same super genes as its sibling is to ensure that there is a group of closely related ancestors line bred in their pedigrees - which have more chance of being inherited by the foal than in a very loose outcross mating where anything can be passed on - - it is an attempt to create more homozygosity in some genetic traits and raise probabilities
It is far more common in showjumping that full siblings have both competed at international level with some full brothers also both being successful at stud.
There are higher heritability factors in showjumping and breeders have a tendency to prefer older proven stallions - this is throwing more opportunity at the foals for an athletic outcome.
Contrast the situation in dressage where much of the time young stallions are all the rage rather than proven producers of GP horses
There is a world of difference in breeding to a spectacular stallion that is himself performing at GP - and breeding to a stallion who is a known producer of GP progeny.
Even if both siblings are successful in sport and / or breeding - due to the rules of genetic inheritance - they cannot possibly have the exact same genetic makeup.
Full siblings may look completely different, or they may have some similar traits - and often similar traits can be observed in families
If we want to weight the percentages given above - in the ancestors up to 6 generations and beyond - we can line breed to a group of closely related superior progenitors throughout the generations in the pedigree. These groups of related ancestors being repeated throughout are going have a far greater impact than their percentages would indicate. If a horse is on the 3rd generation and is repeated at 4 x 6 x 3 x 8 x 7 - as well as close relatives - these percentages will be blown right out of the water
These superior ancestors and their qualities would therefore have a far higher likelihood of being expressed in the foal.
Genes that are in close proximity arre often inheritd together allowing breeders to track specific traits as a group ???
Genes that are physically close together on a chromosome arre more likely to pass togther from parent to foal
Linked genes tend to travel together and are less likely to be separared by crossing over duing meisis
Linebreeding increases the likelihood of passing on linked sets of genes. Closely related ancsors are highly likely to have their genes travel together and be inherited by the foal
Genes tend to be passed down in grouops or bundles rather than as isolated units
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When closely related anecestors rae present both sides of the pedigree, the foal is more likely to receive matching bundles of genes - or haplotypes- from that ancestor
Genes have also been found to travel in clusters or groups - and closely related genes situated near each other on the same chromosome loci have more chance of their traits travelling forward and being available to the foal
This is referred to as Genetic Linkage - where specific desirable traits can be passed down to foals as a group rather than as individual independant traits.
This clustering of close relatives allows breeders to predict certain characteristics in foals by studying the pedigree patterns and tracking the inheritance of these linked multi gene blocks
When 2 genes are close to each other on the same chromosome, there is also lower chance that recombination will happen between them - alleles that are physically close tend to be inherited together - they are said to be linked (Dr Carmen battaglia)
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give examples of full siblings here or leave it out???
The following examples how full brothers in sport and at stud , how there is usually one more successful than the others, even though all may have had good siring careers
It also shows how they differ in type
whether to include with more detail plus pics
Examples of full brothers being successful at stud are World Cup 1 - 111
World Cup 1 was by far the best and most successful brother even though the other 2 did produce useful horses. They also looked considerably different
Welt Hit 1-111
Welt Hit 1 was the most successful at stud and in competition
Voltaire and Concorde -
Pilot and Peter Pan