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In April of 1977 a record of 22.000 spectators Keenland converged to the Kentucky's Racecourse to see a called chestnut-colored filly Sexetary that ran in the third career. She had never competed but it was the favorite one for a single reason: their father." she was the daughter of Secretariat, the first winner of the Triple it Crowns and the biggest purasangre in all the times. Big it was the deception of the miltitud when she was placed in fourth place.

In the following years the descendants of Secretariat didn't stand out and having even served the best mares in the world it never reached the same greatness like reproducer that he possessed, their children (males) neither they were exceptional reproducers. He died in 1989 and it seemed that he closed an important chapter since in their descendant there was not a single outstanding copy as him.

Little before their death the breeders had begun to notice an inclination toward the descendant of their daughters, even those that had never won a career ended up being and they continue being some of the biggest mares sires in the world producing winning pure blood of the most important glasses. The exceptional athletics of Secretariat lives in the second generation of descendants taken place by its daughters.

Per years this phenomenon was popularized so much among the breeders of career horses that when they speak of a copy they always give the name of its parents and that of the maternal grandfather, however didn't have a scientific explanation of reason certain features they jumped a generation and they were passed alone through the females.

Newly in 1997 an article appeared in the Magazine Equus N 242 where there is documentation of the maternal grandfather's scientific evidence. It is hour that the breeders of dogs begin to keep in mind this phenomenon. REVIEWING CONCEPTS We know that each cell of the human body has 39 couples of chromosomes, 50% for the father and the other 50% for the mother. Each chromosome contains thousands of genes that code for different characteristic many of which we can observe (color of eyes, mantel, etc.) that the PHENOTYPE constitutes, what we cannot see is like they are constituted genetically and that is the GENOTIPO. However through the phenotype and with basic knowledge we can predict some genotipos. In those characteristics where it intervenes a single couple of genes and they combine in the Dominant-recessive form it is very simple, I didn't seize in those where many of these couples intervene for a single characteristic (poli genes) and they are exactly those that more they interest us as: angles, color of the mantel, size, etc.


GENETIC EXPERIENCES AND EFFECT OF THE SEX

The theory of Mendel settled down that the sex of the donating gene (father or mother) it was inapplicable in the determination of which gene was expressed, this way if the mother contributed a dominant gene and the father one recessive the dominant one was expressed contributed by the female one and vice versa. They spent more than 100 years until the Dr. Allen in 1969 astonished to the world with a study that seemed to indicate that certain genes could be related to the sex in its expression and in 1986 the Dr. Surani with its experiments in mice concluded that some genes didn't follow the laws of Mendel, however, they are programmed to be activated before the fertilization in a such way that they will always be expressed by their descendants or disabled and they will never be expressed. The factor that determines if that class of genes is passed to the descendant in activated form or disabled it is the SEX of the donors. IMPRINTING OR GENOMIC'S MARKS A hypothesis sustains that a mechanism exists for the one which males and females can control the most essential features. In the fetal development the male's reproductive goal is for example to give the biggest and vigorous descending, but for the female to engender an extremely big foal could be mortal. Perhaps for this reason some critical genes of the fetal development are inactivados for the paternal imprinting, allowing to the genes of the female the complete control on many aspects of the fetal size.


TO JUMP A GENERATION

The imprinting genomic's believes an inheritance pattern whose expression is to jump a generation." To understand this, let us imagine a human gene with paternal imprinting that when it is expressed he gives descending with blue hair, when this gene is not expressed the color of its descendants' hair it is brown.

A man inherits the gene of his mother's blue hair and therefore his hair is blue. As him it is male the gene of the blue hair is disabled to transmit it, this way its male children will inherit the gene in inactive form and all will have brown hair. When their male children reproduce the gene it will remain inactive and all their grandsons (males and women), they will have the brown hair. But when this man's daughters reproduce, the gene in its activated form will make that all their children (males and women) they have the blue hair. Result: the characteristic reappears in the third generation, but only in the descendants of the man's of blue hair daughters.


YOU DOUBT AND DEDUCTIONS
Many doubts are still on this phenomenon and the literature not yet gives us answers of like it can happen. The deductions of this discovery go beyond the world of the career horses. Already a number of human genes with imprinting has been pointed out. The breeders of dogs spread to be impatient and we plows disappointed when extraordinary bad don't it reproduces their excellence immediately, let us remember the maternal grandfather's effect and let us wait to generation.

Dr. Jorge Santoian
THE MATERNAL GRANDFATHER'S EFFECT
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