(B) BREEDING, GENETICS & REPRODUCTION Flashcards
Genetics is used for certain equine activities such as:
Horse racing, reining, cutting, dressage
Horse genetics is used efficiently for
Coat color
Genetic material is stored in Nucleus, DNA, Chromosomes, _____, ______.
gene, locus (loci plural)
How many pairs of chromosomes are found in a horse?
32
TWO PART QUESTION: Of the 32 chromosomes in the horse, how many chromosomes are somatic and how many are sex chromosomes?
31 and 1
TWO PART QUESTION: Give another general term for sex cells and indicate in what specific structures within the ovary and the testes they are found.
Gametes, Egg, Sperm
What term is used to refer to a horse’s genetic blueprint?
Genotype
What is a phenotype?
Appearance of the horse
What is the definition of a diploid?
Entire set of chromosomes located in Somatic (Body) cells 2N=64
TWO PART QUESTION: What is the definition of haploid and what is the haploid chromosome number in the horses?
Half the number of chromosomes found in the sex cells (egg and sperm) N=32
What does the general term ploidy mean?
Either haploid or diploid
What is the purpose of mitosis?
Replication of DNA, and production of 2 identical cells
What is cytokinesis?
Splitting of 1 cell into 2
What is the purpose of meiosis?
To reduce cells chromosomes from diploid (64) to haploid (23)
THREE PART QUESTION: What is another name for meiosis, how many gametes does it produce, and what are those gametes called?
Reductive Division, 4, sex cells
TWO PART QUESTION: Meiosis has 2 divisions. In the first division, how many diploids cells are produced and in the second division, how many total cells are created?
2, 4
In the first stage of meiosis a unique process occurs during which chromosomes swap material. What is this called?
Recombination or crossing over
Genes that are located on same location (loci) on the chromosomes are called what?
Alleles
In reference to genes, define the terms homozygous and heterozygous.
Identical, different
Define dominance and recessive gene
Dominance is the ability of one allele to mask or cover up the recessive allele for the same gene. Recessive allele that is masked or covered by a dominant allele on the same gene
Define qualitative and quantitative gene expressions
Qualitative gene action is influenced by 1-3 gene pairs. Quantitative involves multiple genes influencing a certain trait
Qualitative gene action can be broken down into 3 primary types. Name them.
Dominance, incomplete dominance, codominance
Define incomplete or partial dominance
Neither allele on the gene is dominate, so blending is observed
Define codominance
Both alleles on the gene are dominant, so both alleles are observed
What is the term for when a single gene influences multiple phenotype traits?
Pleiotropy
What type of gene action controls speed in horses?
Quantitative gene action
What is the definition for heritability estimate?
Percentage of a trait that is due to genetics rather than environment
Recombination increases the variability by mixing which genes are grouped together by a gene process called what?
Crossing over
Each gene in the DNA of a cell contains the information necessary to make what?
A protein
Defects in DNA can result in failure to form ____
Essential proteins or proteins that function properly
Defects in DNA can be broken down into 2 main categories. Name them.
Mutant genes, chromosomal aberrations
Mutations in the DNA can lead to ______ and be padded from generation to generation.
Diseases that are heritable
What are the 3 effects of DNA mutations?
Detrimental, beneficial, silent
Define the genetic term ‘silent mutation’
Mutations does not cause a change in the protein seuence
Genetic disease are of 2 types. Name them.
Autosomal genetic diseases on the 31 chromosomes, and Sex Linked is a mutation of the X or Y chromosomes
Genetic lethals are conditions in which the disease is based on the time death occurs. Name and explain the 3 classifications of genetic lethals.
true lethals– death of fetus resulting in abortion
lethal at birth– or shortly after
delayed lethal– occurs later in life
Arabians have a lethal disease of CID- Combine Immunodeficiency Disease that is an autosomal recessive disorder that causes what?
The B and T cells of the Immune System of the foal don’t develop properly and the body is not able to fight off infections. The foal typically dies from respiratory infections by 5 months.
TWO PART QUESTION: Arabian have a Coat Color Dilution Lethal (CCDL) known as what and causes causes what symptoms?
Lavender Foal Syndrome in Arabians– Neurological symptoms (seizures, difficulty standing, abnormal posturing and gait)
What is caused by cerebellar abiotrophy which is found in Arabian Horses?
Purkinje cells in the cerebellum that controls the movement to die
Occipito-Atlanto-Axial malformation in Arabians displays what characteristics?
Occipital bone, C1 (atlas), C2 (axis) of the cervical vertebrae to fuse and cause compression of the spinal cord under one month old. Causes neurological symptoms uncoordinated gait, difficult standing, paralysis of front and hind legs.
TWO PART QUESTION: Causing symptoms in Arabian horses by 6 months of age, juvenile epilepsy is also known as what, and horses may outgrow the condition by what age?
Idiopathic epilepsy, 12-18 months of age.
Overo lethal white foal syndrome is due to what genetic event?
Recessive homozygous overo gene mutation
How many genes mutate to produce the desirable frame overo coloring?
single/one
What is the disease process of lethal white overo syndrome?
There are no nerve cells (ganglion) in the smooth muscle cells in the wall of the intestinal tract, peristalsis does not occur, death within 72 hours.
Hyperkalemic periodic paralysis (HYPP) is an inherited disease due to what trait?
Autosomal dominant mutation from the impressive line
What is the disease process in HYPP (Hyperkalemic periodic paralysis)?
Potassium (K+) levels are elevated in the blood (hyperkalemia), and sodium (Na+) levels rise in the muscle cells that stimulate muscle contraction (twitching). If blood K+ levels continue to rise the muscles are unable to contract leading to paralysis. (Remember Normally Na+ is high in blood, and K+ high inside the cell)
Glycogen branching enzyme deficiency (GBED) is a recessive trait and results in defective ____, death occur shortly after birth.
Storage and function of glycogen in the muscles, heart, brain and liver.
Polysaccharide Storage Myopathy (PSSM) is a dominant disease that results in what?
Muscle weakness and atrophy, Dietary restriction of carbohydrates can control the symptoms.
TWO PART QUESTION: Hereditary Regional Dermal Asthenia (HERDA) is what type of autosomal disorder and affects what specific part of the body?
Recessive, connective tissue due to collagen defect.
What is the disease process of HERDA
At age 2-3 hyperelastic skin that easily tears
HERDA is common in what equine discipline?
Cutting horses where 30% of the elite sires are heterozygous for this disease.
Quarter horse sire Poco Bueno is associated with what genetic disease?
HERDA
Epitheliogensis Imperfecta is what type of fatal genetic disease?
Autosomal recessive
Genetics along with environment define what?
Phenotype of an individual
DNA is composed of 4 nucleotides. Name them.
Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
What genetic term describes when changes to the nucleotide sequences occurs as the cells divide and long DNA molecules are replicated?
Mutations
Bay is a basic coat color and is the result of interaction of wild types alleles which two loci or genes?
Agouti (ASIP), and Extension (MCIR)
What specifically about black pigment expression does the Agouti gene control?
Where it is expressed
Which gene allows black pigment to be expressed in the first place?
Extension gene
Using A for Agouti and E for extension, state how a bay horse’s genotype would be written for both homozygousity and heterozygousity.
AAEE (homosygous) or AaEe (Heterozygous)
A chestnut color horse has what genes?
ee (no Extension gene that expresses the black pigment)
A black horse has what genes?
aaEe or aaee
Other coat color genes are separate from the Agouti and Extension genes but the effect they have on the Horses’s color depends on what loci?
A and E loci
The major color dilution mutations have what genetic action?
Dominant
Silver, Dun, Champagne, and Cream Dilution are the major what?
Dilution mutations
When a Chestnut horse inherits 1 copy of the Cream (CR) Dilution the horse will be what color?
Palomino
When a Chestnut horse inherits 2 copies of the Cream (CR) Dilution it is what color?
Cremello
Because there is an additional dilution effect when 2 cream are inherited, the cream dilution is classified as what kind of dominance?
Incomplete.
A bay horse that has 1 CR gene becomes what color?
Buckskin
A bay that has a homozygous genes for CR is what color?
Perlino
The Champagne (CH) dilution produces what color on a chestnut?
Golden
The silver dilution gene works on which pigment?
Black
The silver dilution gene is common in which breeds.
Shetland ponies and Rocky Mountain horse
Dun is a dominant dilution gene (D_) and is known as what type of color of the horse?
Original wild color
Non-dun horses have 2 gene mutations on what gene?
TBX3 gene
A bay dun is distinguished by what phenotypic coat characteristic?
Dorsal stripe along the backbone
What are color terms are used to refer to black horses with the dun factor
Grulla/grullo or black dun
The term Paint is reserved for horses of what type of lineage?
Quarter Horse or Thoroughbred
Which color pattern mutation produces all white horses when homozygous, but is not lethal?
Sabiino mutation (SB-1)
Three of 4 mutations for which color pattern occur in the MITF gene (SW1) ?
Splashed white
The splashed white phenotype has been associated with what health condition?
Deafness
Tobiano is a spotting pattern caused by chromosome rearrangement involving the K IT gene and has what type of gene action?
Dominant
Which color pattern occurs when a mutation in the TRPM1 gene occurs on the LP1 locus, results in the amount of white expressed varying and is dominant?
Appaloosa
Congenital Stationary Night Blindness (CSNB) is a condition from which homozygotes of which mutation suffer?
LP1 mutation (Appaloosas)
TWO PART QUESTION: Roan has what type of gene action and thus requires what number of parents to be phenotypically roan for the offspring to express roan?
Dominant, one
The gray mutation had what type of genetic action?
Dominant
As gray horses age, the loss of pigment from the hair follicles happens in what manner?
Gradually
Why would a Caslick’s operation is performed on a mare?
Because the mare has pneumovagina, a condition that maybe inherited, feces, air and debris are sucked into the internal reproductive tract.
A cervix that is pink and so relaxed that if it is found lying limply of the vaginal floor facilities what process that is necessary for conception?
Passage of semen
The uterus is suspended within the body cavity by what structure?
Broad Ligament
Located longitudinally and circularly, the middle layer of the uterus is called what?
Myometrium
Which layer of the uterus is important for the transfer of nutrients to the placenta?
Endometrium
The oviduct has three layers, name them
infundibulum, ampulla, isthmus
What is the part of the oviduct where fertilization normally occurs
Ampulla
The more muscular part of the oviduct is what?
Isthmus
TWO PART QUESTION: The fimbriae is at the end of which part of the oviduct and what is it’s purpose?
Infundibulum, catches the egg (ovum) when released from the ovary
What is the wedge shaped area of the ovary from which the ovum may be ovulated.
Ovulation fossa
The medulla and cortex are where on the ovary?
Medulla is on the outside and the cortex is the inside with undeveloped follicles.
List the stages of follicular development from smallest to largest.
Primordial follicle, secondary follicle, tertiary follicle, Graafian follicle.
TWO PART QUESTION: Which developmental stage of the follicle secrets estrogen, and what is estrogen’s purpose?
All the follicles do as they grow, which tell the mare she is ready to be bred
TWO PART QUESTION: the corpus luteum (CL) produces what hormone which serves what purpose?
Progesterone that prepares her body for pregnancy.
What does seasonal polyestrus mean?
During the spring and summer, the mare will have estrus cycle every 21-23 days.
There are 4 stages of the estrous cycle, name them from start of the new cycle.
Proestrus, Estrus (ovulation), metestus, Diestrus (14-1 days)
Which estrus cycle produces progesterone
Diestrus
What part of the midbrain is responsible for receiving intrinsic and extrinsic messages and coordinating those signals for reproduction?
Hypothalamus
TWO PART QUESTION: The hypothalamus releases what hormone which triggers the Anterior Pituitary to release what 2 hormones?
Gonadotropic Releasing Hormone (GnRH), Ant Pituitary releases Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
FSH stimulates what specifically?
Growth of the follicles in the ovary
Luteinizing Hormone (LH) is responsible for what?
Stimulating ovulation and supporting initial stage of Corpus Luteum (CL) development
The circulating progesterone in the blood reaches the pituitary gland and triggers what action?
Inhibits the release of LH which stops the estrus cycle
TWO PART QUESTION: If the mare does not become pregnant, 14-16 days after ovulation the uterus releases what hormone which causes what to happen
Prostaglandin F2alpha that destroys the corpus luteum (CL) and follicle development in the ovary starts again.
Melatonin is triggered by environmental factors (sunlight) that signal the Hypothalamus to release what?
Gonadotrophin Releasing Hormone (GnRH)
The testicle like the ovary is both a ___ and a ____ that produces hormones and additionally serves as the site of spermatogenesis.
Exocrine and Endocrine
A stallion’s testicles lie in a horizontal axis for what reason?
Ease of the movement for the stallion
In degrees celsius, how much lower than normal body temperature must the process of spermatogenesis occur at?
4-6 degrees celsius
What is ridgeling or cryptorchid?
Testicle retained in the abdomen (undesended)
Membrane of the testicular sac that is smooth muscle and has the ability to raise the testes closer to the body?
Tunica dartos
This muscle is in the spermatic cord also helps maintain proper temperature.
Cremaster muscle
Incoming blood in the arteries is cooled by the artery vein contact in the spermatic cord is called ____.
Pampiniform plexus
The epidiymis is a bundle of convoluted epididymal ducts and has 3 parts.
Head (caput), body (corpus), tail (cauda)
TWO PART QUESTION: Immature sperm enter the epidiymis at what region and mature in what region?
Head (caput) and mature in the body (corpus), tail (cauda)
The ampulla is a widen area of what structure located just before the urethra?
Vas deferens (ductus deferns)
Name the accessory sex glands
Vesicular glands (seminal vesicles), prostate gland, bulbourethal glands (Cowpers glands)
TWO PART QUESTION: Semen has three fractions- the first fraction is the pre-sperm fraction. What function does it serve and from where does it originate?
From the bulbourethral origin and functions in cleansing the urethra
Which of the 3 seminal fraction contains 45-75% of the spermatozoa
Second or middle fraction
TWO PART QUESTION: What is the name and description of the third fraction of the semen?
Gel Fraction is a clear viscous fluid is the third fraction.
What fraction of the semen is not used (discarded) in artificial insemination (AI)?
Third Gel fraction complicates AI
Give the term that means penis is spongy and cavernous allowing it to fill with blood during erection.
Musculocavernous
What cells of the testes are affected by FSH (Follicle Stimulating hormone) and testosterone?
Sertoli cells
What cells of the testes are affected by LH (Luteinizing Hormone)?
Leydig (interstital cells)
What cells produce testosterone?
Leydig (interstital cells)
What hormone is produced by the Sertoli cells and what is the action?
Inhibin- inhibits the production of FSH
Libido is triggered by what hormone?
Testosterone
The term that describes striking, biting, willingness to see out, mount and breed mares?
libido
What does the term proud cut mean?
Actually no such thing
What are the 3 reasons a gelding will exhibit stallion behaviors?
Behavior is learned, only 1 descended testicle, or the adrenal gland which produces gonadocoriticoids is affecting behavior
The behavior a stallion demonstrates at the completion of ejaculation, with up and down movement of the tail
Flagging
The approximate number days the entire process of spermatogenesis.
60 days
Spematogensis is a(n) ______, ongoing process (contrary to the mare) that makes the millions of sperm.
Meiosis
Stallions have a minimum number of spermatozoa produced in a 24 hour period called _____.
Daily Sperm Production (DSP)
The Daily Sperm Production varies among stallions because of what 2 factors?
Testicular size, season (increased in spring and summer, but make sperm all year long.)
Name 2 types of group teasing methods
Cage or box teasing and teasing chute
Name 2 types of individual teasing methods
Stall and rail
How many minutes of teasing, when using a stallion cage, is required to allow all mares an opportunity to demonstrate estrus behavior?
15-20 minutes
There is a scoring system for behavioral estrus in mares. What is the difference between an estrus score of three and four?
3: interest in stallion is shown through facial expression, tail raising, flexing of the pelvis, winking and urination.
4: turning of the hindquarters and leaning of the hindquarters to the stallion
What is the most effective method for manipulation of the estrous cycle?
Extended day light artificially
TWO PART QUESTION: When using artificial lighting to manipulate the Estrous cycle how many hours of light per day are required and in which months is the artificial lighting used?
16 hours of light, 8 hours of dark, in the months of late November to early December for estrous cycle to start in mid to late February
The amount of light elicit photoperiodic stimulation is at least 3 foot candles at level of horse’s eye. This is equivalent to what watt and type of light bulb?
200 watt incandescent bulb
TWO PART QUESTION: How many days after an artificial lighting program is initiated is a behavioral estrus response is seen AND does ovulation occur?
30-60 days after light program, 60-90 days after light program for ovulation
What is a side effect of an artificial lighting program?
Shedding
Name the 3 most common exogenous hormones used to manipulate the estrous cycle?
Prostaglandid, Human chorionic gonadotropin, and progesterone.
TWO PART QUESTION: Why is prostaglandin the most widely used hormone in exogenous hormone therapy for manipulating the estrous cycle and when during the cycle is it given?
It shortens the mare’s cycle by approximately 1 week, it is given 5-6 days after ovulation.
HCG (Human Chrionic Gonadotrophin) usually results in ovulation withing how many hours?
48 hours
Pneumovagina is the primary cause of what in broodmares?
Uterine infections
This operation sutures the upper portions of the vulva together to prevent dirt and fecal matter to enter he vagina.
Caslicks’s operation
The ideal body condition score for broodmares is what?
5-7
TWO PART QUESTION: What problem do thin mares have with pregnancy and what 2 problems do obese mares with pregnancy?
Thin mares: Getting and maintaining pregnancy.
Obese mares: have lower milk production and focal growth.
How frequently should mares be monitored throughout pregnancy and lactation?
Weekly monitored
How many days prior to foaling should mares be removed from Fescue pastures?
60-90 days
Pregnant mares eating tall fescue in pasture have potential to exhibit what symptoms?
Agalactia (inability to produce milk), prolonged gestation, thickened placenta, redbag deliveries, retained placenta, dystocia (difficulty giving birth).
What core vaccinations are recommended for the broodmare?
Tetanus, Eastern and Western Encephalomyelitis (EEE/WEE), West Nile Virus (WNV), and Rabies
Vaccinations provide protection for_____.
Mare and newborn foal
What type of immunity do foals acquire through the ingestion of colostrum?
Passive immunity or passive transfer of immunity
A foal’s immune system is not fully functional until how many months of age?
2-4 months
TWO PART QUESTION: Colostrum is secreted by the mare for how long after parturition and is only able to be absorbed by the foal’s digestive tract for how long after birth?
24 – 48 hours mare, 36 hours after birth
Name four signs that a mare is approaching parturition.
Size of udder (2 weeks before), waxing – sticky secretions develop on the teats of the mare (24 hours), abdomen enlarged and dropped, softening of muscles and ligaments near tail head.
What are the signs of Stage 1 of foaling?
Signs of discomfort/agitation, walking aimlessly, lying down and standing up, sweating, overall restlessness.
Stage 1 ends when this happens.
Water breaks
TWO PART QUESTION: Just before parturition, in what position is the foal in and during Stage I for parturition the foal rotates to what position for delivery?
Dorsopubic – upside down, and rotates to dorsosacral – upright position with spine upwards.
Describe the normal presentation of the foal
Silvery-white sac appears with front feet coming out first, and hooves facing down, followed by the nose of the foal.
Stage II of foaling ends when what happens?
Birth of foal
TWO PART QUESTION: What is the most difficult part of Stage II of foaling, and how long should this stage take?
Delivering the shoulders, 20-30 minutes for Stage II birth of foal
TWO PART QUESTION: Stage III of foaling is the final stage which should be complete within what time frame and concludes when what happens?
Delivery of placenta delivery in 3 hours (do not pull or tear placenta)
What is the proper way to aid in the breaking of the umbilical cord?
Never cut, it bleeds more, wrap the cord around 2x your finger press on the foal’s abdomen and tear. Never pull umbilical cord directly against foal’s abdomen.
TWO PART QUESTION: How often should the umbilical stump be dipped and with what?
Several times the foal’s first day of life, with 2 % Iodine.
Doing what helps a foal who is slow to find the mare’s udder?
Rubbing their croup, Foals should nurse within 2-3 hours.
What is colostrum made up of?
Nutrients high in energy, protein (Immunoglobulins (antibodies) in this fraction), minerals, vitamin A, laxative.
In what position does a foal in pain rest?
Sits upright resting on its chest, curls its legs and neck in an unusual position or roll onto its back
How many times per hour will a normal foal nurse?
7
What are the TPR numbers for a foal in the first 4 days of life?
99-102 degrees F, Heart Rate 70-100 beats/min (excited), resting respiration is 20-40/min
After 2 months of age the foal will need to have supplemental feed fed by what device to prevent the dam access.
Creep feeder
Foals fed in excess of their requirements are at an elevated risk for?
Developmental disorders
Foals are normally weaned at how many months of age?
4-6 months
