(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