Page 44 - 8 June 2012 Special Broodmare Edition

primary role of the nuclear DNA is to supply the 32 chromosome pairs that make up the genetics or genotype of the individual. The mitochon- drial DNA functions to regulate the mitochon- dria’s ability to supply energy to the cell.
What makes mitochondrial DNA unique is that it is passed only from the mother to her offspring. That is another key to increas- ing the maternal influence of the mare. No mitochondria DNA is found in the sperm head, but there is some in the tail of the sperm. However, the mitochondrial DNA in the sperm is lost upon fertilization when the sperm tail drops off, so the stallion does not pass on any mitochondrial DNA to his off- spring. This means that all horses descended from the same female in the tail female line have the same mitochondrial DNA.
The mitochondrial DNA contains groups or sets of genes called haplotypes that are passed down together from generation to generation. This is what ties the families together as these haplotypes go through very little change. Thus we have another genetic link between a mare and her produce that is not controlled by the sire.
One ongoing theory is that a horse’s speed and/or stamina is rooted in the mitochondrial DNA and therefore comes down the tail female line. Several companies have identi- fied a number of genes that help breeders determine the potential racing capabilities of their horses. These companies profess that the aptitude of a horse to run a specific distance or class of race is controlled by a number of factors, with the base of their research focused on the role of the mitochondrial DNA.
Determining exactly how mitochondrial DNA affects athletic performance is a highly sought out goal for human and animal genet- icists. Differences in the genetic informa- tion between horses of varying performance ability gives us food for thought into the importance of the mitochondrial DNA and the role it plays in performance ability.
Three Bars is a good example. Three
Bars traces in his tail female line to the Layton Barb Mare who supplied the original mitochondrial DNA for this family. This
is family number four of the Bruce Lowe Figure System that ranked the top 50 foundation mares in the production of major races like the English Derby. This is the same family that has produced such noted mares as Maggie BB, who counts among her foals Iroquois, the first American bred to win the English Derby; Mahubah, the dam of Man O War; and Alice Hawthorne, the dam of Thormanby, who sired Rouge Rose, the dam of the famous Bend Or and Marquerite,
the dam of Triple Crown winner Gallant Fox. Maggie BB also produced Jaconet, the dam of Sir Dixon, found in Three Bars’ pedi- gree. One source of speed that comes from this tail female line is *Epinard, who was the sire of Hygro, an early source of speed for Quarter Horse breeders.
Tesio’s mare Catnip is also from family #4. She is a tail female descendant of the Layton Barb Mare. This means her famous grandson Nearco is from the same family.
THE X AND Y RELATIONSHIP
The majority of our genetic information
is carried on 32 pairs of chromosomes found in the nuclear DNA. Science tells us that each parent contributes 32 chromosomes to the foal, giving the horse 64 chromosomes (32 pairs). But are all things equal? A look at the sex chromosomes will answer that question.
The sex of a foal is determined by the sex chromosomes, identified as X or Y. The chro- mosome makeup for a male is a combination ofanXandaY,theXcomingfromthe mother and the Y coming from the father. The genetic makeup of the sex chromosomes for a female is two Xs—an X from her father and an X from her mother.
Geneticists say the Y chromosome has less genetic material to pass on to the next
generation. That means a mare has more potential influence on her sons through a greater amount of her genetic material being passed on with her X chromosome.
Many stallions are given the title of “broodmare sire” due to the success of their daughters. The genetic relationship between a stallion and his mother may give us an explanation for some of the stallion’s abil- ity to sire good broodmares. The stallion receives his Y chromosome from his sire and his X chromosome from his dam. He passes his X on to his daughters. This creates a direct genetic link between the broodmare sire, his dam and his daughters.
Three Bars became a great sire with his record showing that he sired 14 AQHA racing champions. But he was also a noted broodmare sire. His daughters produced the earners of $7,021,235 including Easy Jet ($445,723). Three Bars inherited his X chromosome from his dam Myrtle Dee and he passed that X on to his daughters.
Easy Jet, the 1969 AQHA Racing
World Champion, is out of Lena’s Bar, a Thoroughbred daughter of Three Bars. Easy Jet went on to be a successful sire and brood- mare sire. Through 2011 he is the No. 3 All- Time Leading Money Earning Broodmare Sire. His maternal grandget have earned $51,286,213 and include All American Futurity winner Eastex. Easy Jet inherited his X chromosome from his dam, Lena’s Bar, by Three Bars. We don’t know if the X chromo- some Easy Jet inherited was from Lena’s Bar’s sire or dam, but it is interesting to speculate.
Lena’s Bar is double bred to Percentage, the sire of Three Bars and Perhobo. Perhobo is the dam of Lena Valenti, who was the dam of Lena’s Bar. There is the possibility that Percentage could have supplied an X to Lena’s Bar through his daughter Perhobo. Lena’s Bar is a great broodmare, and no mat- ter which X she gave Easy Jet it must have been a good one.
Lena’s Bar TB contributed greatly to the Quarter Horse breed as the dam of Easy Jet.
LENA’S BAR TB
Three Bars
Percentage
Midway
Ballot
Thirty-Third
Gossip Avenue
Bulse
Rosewood
Myrtle Dee
Luke McLuke
Ultimus
Midge
Civil Maid
Patriot
Civil Rule
Lena Valenti
Gray Dream
*Gino
Tetratema
Teresina
Dark Love
*Traumer
Sunny Love
Perhobo
Percentage
Midway
Gossip Avenue
Homebody
General Thatcher
*Scramble
42
SPEEDHORSE, June 8, 2012
It is interesting to see that Percentage passed his X on to his daughter Perhobo and that could have been passed on to Lena’s Bar through her dam Lena Valenti.
Speedhorse Files