THE X-FACTOR IN RACEHORSES
WHAT IS THE X?
The X is a chromosome that is carried through the
female only. A male (of any species, Human, Horse, Cow, Dog, etc.) carries
one Y chromosome and one X chromosome. A male is identified as YX. A female
carries two X chromosomes. (Female =XX) When a male and female conceive
the offspring has to inherit these chromosomes to decide what sex it will
be. In other words, if the offspring picks up the Y from its sire, it will
be a male. If it picks up the X from her sire it will be a female. No matter
what, the offspring will always carry an X chromosome.
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YX
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YX
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XX
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YX
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YX
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XX
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XX
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YX
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YX
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XX
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XX
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YX
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XX
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XX
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WHY IS THIS IMPORTANT?
It has been proven that the heart size of an athlete
can enhance performance.
In Australia, they did a retrospective study of
Thoroughbreds. The conclusion of this study came to an astounding figure.
They found that 89% of high-class winners had large heart scores. Compare
this to the general population where only 25% of horses have large heart
scores, the results are very exiting indeed!!
One must remember, however, that the heart size
of a horse can only provide results if other factors are in play. Research
has concluded that 22-23% of a horse's ability comes from it's heart score.
This means that approximately 77% comes from other factors. These could
be conformation, training techniques, feed, disposition, and numerous other
factors in a horses day to day routine. One must always remember and give
credit to the human intervention and influence to a horses performance.
FOLLOWING THE HEART LINE IN PEDIGREES
Like I noted before, the mare carries two X chromosomes.
She gets one from her dam and one from her sire. The stallion carries one
X chromosome, which he receives from his dam and passes to his daughters.
His Y chromosome is passed only to his sons, that he, in-turn, received
from his sire. The large heart is passed through the X chromosome, thus
a sire cannot pass this on to a son. He can only pass his X chromosome
to his daughters. This might explain the erratic behavior of the sire-line.
Since high-class performance is linked to the heart size, and heart size
has recently been proven to come from the X chromosome, it makes one wonder
how much importance a sire-line(the "Y" line) really is. Not to say some
positives don't come from the male line, just maybe the fact that too much
emphasis has been placed on the male-line and not enough on the female
line. Of course, they didn't have the genetic knowledge that modern breeders
now have in their hands to use. The lack of this knowledge had many breeders
of the past perplexed. Why a brilliant son of a brilliant stallion couldn't
produce another son of great ability had many breeders write the stallion
off as a failure. Only after many years, did they realize the genetic potential
of the stallion when his daughters started producing superior runners.
The perfect example of this is Secretariat.
Following the X line in pedigrees is actually quite
simple. You first must know the sex of the horse you are studying. It may
seem confusing to explain in words so I have set up tables to visually
show the pattern. First I will start with a male:
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YX
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YX
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XX
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YX
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YX
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XX
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XX
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YX
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YX
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YX
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XX
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XX
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YX
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XX
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XX
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Female:
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YX
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YX
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XX
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YX
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YX
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XX
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XX
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XX
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YX
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YX
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XX
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XX
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YX
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XX
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XX
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THE 4 LARGEST HEART LINES, AND SOME MODERN STALLIONS
CARRYING THEM
PRINCEQUILLO
A.P. INDY, ACK ACK, AFLEET, AL MAMOON,BECKER,BOLD
BIDDER, CHEIF'S CROWN, CORPORATE REPORT, DANZIG CONNECTION, DEFENSIVE PLAY,
DEHERE, DIPLOMAT WAY, DIXIE BRASS, DR. BLUM, FARMA WAY, FAST GOLD, FORTY
NINER,GONE WEST, KEY CONTENDER, KEY TO THE MINT, KRIS.S, MILL REEF, MOSCOW
BALLET, MOUNTAIN CAT, ONE FOR ALL, PARTY MANNERS, PLEASANT COLONY, QUACK,
ROBIN DES PINS, SECRETARIAT, SHAM, SIR GAYLORD, SLEW CITY SLEW, SOMETHINGFABULOUS,
STORM CAT, SUCCESOR, SUMMER SQUALL, SWORD DANCE, TOM ROLFE.
WAR ADMIRAL
ACADEMY AWARD, AFFRIMED, ALLEN'S PROSPECT, ALYSHEBA,
BELIEVE IT, BET TWICE, BETTER SELF, BROAD BRUSH, BUCKPASSER, BUPERS, CAHILL
ROAD, CRAFTY ADMIRAL, CRYPTOCLEARANCE, CURE THE BLUES, DESERT SECRET, DR.
FAGER, EASY GOER, EL GRAN SENOR, FAPPIANO, FAST PLAY, GREAT ABOVE, HOIST
THE FLAG, HOUSEBUSTER, IRISH OPEN, LOMOND, MINING, PERSONAL FLAG, PLUGGED
NICKEL, PRIVATE ACCOUNT, QUIET AMERICAN, RARE PERFORMER, SEATTLE SLEW,
SEEKING THE GOLD, SILENT SCREEN, UNBRIDLED, SWAPS, SWEEP, WAVERING MONARCH,
WHIRLAWAY, WITH APPROVAL, WOODMAN
BLUE LARKSPUR
ALLEGED, ALYDAR, ALYDEED, BATES MOTEL, BATONNIER,
BIG SPRUCE, BLUSHING JOHN, BOLD REASON, BOLDNESIAN, BUCKPASSER, CAVEAT,
COHOES, DAMASCUS, DAYJUR, DEVIL'S BAG, FLY SO FREE, GREEN DANCER, GREY
DAWN II, HALO, LITTLE MISSOURI, MR. PROSPECTOR, NIJINSKY II, PERSONAL HOPE,
PRINCE JOHN, RED RANSOM, RELAUNCH, RIVERMAN, ROBERTO, SEATTLE SLEW, SKYWALKER,
SLEWPY, SMILE, STALWART, T.V. LARK, ZANTHE
MAHMOUD
ARAZI, DEMON'S BEGONE, FLYING CONTINENTAL, GALLANT
MAN, GRAUSTARK, GREY DAWN II, HALO, HIS MAJESTY, HOLY BULL, HOMEBUILDER,
MAJESTIC PRINCE, MICKEY MCGUIRE, NORTHERN DANCER, OPENING VERSE, PINE BLUFF,
RAHY, RAINBOWS FOR LIFE, RISEN STAR, SILVER GHOST, SIR HARRY LEWIS, SKIP
TRAIL, SOVEREIGN DANCER, SPECTACULAR BID, STATE DINNER, TASSO, WAQUOIT,
WHAT A PLEASURE
SOME "DOUBLE COPY MARES"- LARGE
HEARTED MARES THAT CARRY THE LARGE HEARTED GENE ON BOTH X CHROMOSOMES
ALCIBIADES, ALLUVIAL, ALMAHMOUD, ALTHEA, ARAUCARIA,
ASPIDISTRA, BABY LEAGUE, BATHING GIRL, BE FAITHFUL, BEE MAC, BEL SHEBA,
BELTHAZAR, BETTY'S SECRET, BIRD FLOWER, BLACK HELEN, BLOODROOT, BLUE BANNER,
BLUE DENIM, BOAT, BOUDOIR II, BRAMALEA, BROADWAY, BRUSHUP, BUSANDA, BUSHER,
BUSINESSLIKE, CAP AND BELLS, CHAPEL OF DREAMS, CON GAME, COSMAH, COSQUILLA,
COURTLY DEE, CRIMSON SAINT, FALL ASPEN, FLAMING PAGE, FLITABOUT, FLOWER
BOWL, GAGA, GANA FACIL, GAY MISSILE, GLORIOUS SONG, HOPESPRINGSETERNAL,
IMPERATRICE, KERALA, KEY BRIDGE, KILLALOE, LA TROIENNE, LADY ANGELA, MILLICENT,
MISS CARMIE, MISS ZIGBY, MISTY MORN, MOCASSIN, MUMTAZ BEGUM, MUMTAZ MAHAL,
MY CHARMER, MY DEAR GIRL, MYRTLEWOOD, NATALMA, NAVAL ORANGE, NOBLE LASSIE,
NUMBERED ACCOUNT, PERSONAL ENSIGN, PLUCKY LEIGE, PRAYER BELL, QUICKLY,
RARE MINT, RELAXING, ROMANELLA, ROUGH SHOD II, SECRETAME, SELENE, SEQUENCE,
SHARON BROWN, SHY DAWN, SIX CROWNS, SOLAR SLEW, SOMETHINGROYAL, SOUTH OCEAN,TAMERETT,
TELERAN, TERLINGUA, TOLL BOOTH, WAVY NAVY, WON'T TELL YOU
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