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The Breeding Systems cont…. The horse’s 64 chromosomes (32 pairs) come together when the sire and dam are mated. The sire provides 32 chromosomes and the dam provides the other 32. The gene's location is fixed on the chromosomes and combines with another genes at that location when the embryo is formed. The two genes are called alleles. When the alleles are identical in their code, they are homozygous. If they are different they are said to be heterozygous. How do we get homozygosity? We inbreed. Inbreeding leads to an increase in homozygosity of the gene combinations. Bakewell developed his desired type by inbreeding which lead to homozygosity of the desired traits. This allowed the traits to be passed on generation after generation. The homozygous state is seen in such traits as the white faces of Hereford cattle. The Hereford breeds true for this trait. Even in crossbreeding with Angus cattle, the white face is expressed because the Hereford passes only that trait on and it is dominant in nature. (The white face masks the black face of the Angus.) A key beneficial effect of homozygosity is the phenomenon we know today as prepotency. Prepotency is defined as the ability of an animal to mark his or her foals with desired characteristics. Color and markings are the most identifiable characteristics of the prepotent individual.

owner wanted “because the mare owner knew what he wanted” and Leo would give it to them. He then went on to point out that Leo would cross with mares from many bloodlines including Joe Hancock, King, Three Bars and Oklahoma Star sire line mares.

with Angus cattle, the white face is expressed because the Hereford passes only that trait on and it is dominant in nature. (The white face masks the black face of the Angus.)

A key beneficial effect of homozygosity is the phenomenon we know Where did Leo’s prepotency today as prepotency. Prepotency is come from? Well a look at his pedigree defined as the ability of an animal to will define what we are talking about mark his or her foals with desired with inbreeding and it’s role in homo- characteristics. Color and markings zygosity making the individual prepo- are the most identifiable characteristent. Leo was sired by Joe Reed II by tics of the prepotent individual. Joe Reed P-3 and out of Little Fanny by Joe Reed P-3. This is a half The greatest example of the phebrother/sister mating that apparently nomenon of prepotency in the quarter resulted in Leo inheriting a lot of the horse comes through Leo. Leo’s prepogood genes from Joe Reed P-3 making tency or his ability to mark his foals in him homozygous for those genes ena- the quarter horse industry is legenbling him to pass them on. dary. Leo’s long time owner and his fellow AQHA Hall of Fame member The animal's physical character- Bud Warren talked about it this way, “Leo was a combination of genes the istics are his phenotype or what he clicked.” Warren went on to explain looks like. His genetic makeup is that he could breed any mare the mare known as his genotype. owner wanted “because the mare The horse’s 64 chromosomes (32 owner knew what he wanted” and Leo would give it to them. He then went on pairs) come together when the sire and dam are mated. The sire provides to point out that Leo would cross with mares from many bloodlines including 32 chromosomes and the dam provides the other 32. The gene's location Joe Hancock, King, Three Bars and Oklahoma Star sire line mares. is fixed on the chromosomes and combines with another genes at that Where did Leo’s prepotency location when the embryo is formed. come from? Well a look at his pedigree The two genes are called alleles. When the alleles are identical in their will define what we are talking about with inbreeding and it’s role in homocode, they are homozygous. If they zygosity making the individual prepoare different they are said to be hettent. Leo was sired by Joe Reed II by erozygous. Joe Reed P-3 and out of Little Fanny by Joe Reed P-3. This is a half How do we get homozygosity? We inbreed. Inbreeding leads to an brother/sister mating that apparently increase in homozygosity of the gene resulted in Leo inheriting a lot of the good genes from Joe Reed P-3 making combinations. Bakewell developed his him homozygous for those genes enadesired type by inbreeding which lead bling him to pass them on. to homozygosity of the desired traits. This allowed the traits to be passed on generation after generation.

The greatest example of the phenomenon of prepotency in the quarter horse comes through Leo. Leo’s prepotency or his ability to mark his foals in the quarter horse industry is legendary. Leo’s long time owner and his fellow AQHA Hall of Fame member Bud Warren talked about it this way, The homozygous state is seen in “Leo was a combination of genes the such traits as the white faces of Hereclicked.” Warren went on to explain ford cattle. The Hereford breeds true that he could breed any mare the mare for this trait. Even in crossbreeding Volume 1, Issue 1

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