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Animal Genetics
Natural Selection
an organisms ability to SURVIVE and pass on its GENETIC information to its offspring.
Artificial Selection
HUMAN control over organisms passing on their GENETIC information.
Heredity
the POTENTIAL an organism has to show certain TRAITS due to its GENETIC information
Environment
the EXTERNAL conditions that affect the traits and PERFORMANCE of an animal
Environment vs. Heredity
An organism's traits and performance are a sum total of its ENVIRONMENT acting upon its GENETIC information.
Environment vs. Heredity
Some TRAITS are influenced more by an organism's ENVIRONMENT than by its GENETICS, while others are influenced more by genetics.
Heritability The percentage that a trait is affected by
its genetic information is called HERITABILITY.
A heritability factor of 0.0 means that a trait is influenced very little by genetic information
A heritability factor of 1.0 means that a trait is influenced very little by the environment.
Examples of Heritability
Birth Weight = .40 Weaning Weight = .30 Multiple Births = 0.0 - 0.10 Dressing Percentage = .60
Adaptability
The ability of a BREED to become SUITABLE to specific environmental conditions
Type
a group of ANIMALS that are grouped together according to the PRODUCTS they produce
Examples -- Beef type cattle, Dairy type cattle, Wool type sheep, Mutton type sheep
Species
a group of ORGANISMS that have several common CHARACTERISTICS that differentiate them from others.
Scientific Names of Species
Cattle: Bos taurus, Bos indicus Sheep: Ovis aires Swine: Sui suidae Horse: Euquis caballus Chickens: Galus galus
Breed
animals having a common ORIGIN and CHARACTERISTICS that distinguish them from other groups within the same SPECIES.
Purebred
individuals within a BREED. They must have all of the CHARACTERISTICS of the breed and have a recorded PEDIGREE.
Pedigree
a record of an individual's ANCESTRY.
Breeds of Cattle
Angus
Angus
Hereford
Charolais
Charolais
Brahman
Brahman
Shorthorn
Shorthorn
Simmental
Simmental
Salers
Salers
Texas Longhorn
Red Angus
Limousin
Belted Galloway
Beefmaster
Holstein-Friesian
Holstein-Friesian
Guernsey
Jersey
Breeds of Sheep
Rambouillet
Rambouillet
Columbia
Suffolk
Suffolk
Hampshire
Merino
Dorset
Lincoln
Breeds of Swine
Duroc
Hampshire
Chesterwhite
Yorkshire
Landrace
Production of Sex Cells (Meiosis) 1. SIMILAR events to mitosis 2. Occurs ONLY in the TESTES and
OVARIES to produce egg and sperm cells. 3. REDUCES the NUMBER of
chromosomes to half the normal number. 4. ONE replication followed by TWO cell
divisions.
Meiosis
FERTILIZATION
the union of the egg and sperm nuclei
restores the normal chromosome number.
ZYGOTE
a fertilized egg
SPERMATOGENESIS
1. occurs in TESTES 2. EQUALLY sized cells 3. FOUR sperm cells produced
Spermatogenesis
OOGENESIS
1. occurs in OVARIES 2. DIFFERENT sized cells 3. ONE egg cell produced and
three POLAR bodies
Oogenesis
Patterns of Inheritance
DOMINANT the trait that SHOWS in a cross
between two true-breeding parents
Example in Cattle -- Black coat color, polled
Example in Sheep -- White wool Example in Swine -- Black hair
Recessive
the trait that is HIDDEN in a cross between two individuals.
Example in Cattle -- Red coat color, horns, dwarfism
Example in Sheep -- Black wool Example in Swine -- Red hair
PHENOTYPE
the OUTWARD appearance of the organism
Genotype
the actual GENE MAKEUP of an organism
Homozygous
when both of the genes (letters) in the pair are the SAME
Example -- TT or tt
Heterozygous
when both of the genes (letters) in the pair are DIFFERENT
Example -- Tt
Incomplete Dominance
The genes are neither dominant nor recessive, but are equals
Example -- Shorthorn Cattle
–WW=White
–RR=Red,
–RW=Roan
Types of Mating Systems
Purebred Inbreeding Linebreeding Outcrossing Grading up Crossbreeding
Hybrid vigor
increased performance of offspring over that of the parents when unrelated individuals are mated.
Heterosis
Performance Pedigrees
summarizes a particular animal's own performance records as well as records of ancestors, siblings, and progeny.
Progeny = offspring
EPD
EXPECTED PROGENY DIFFERENCE
an INDICATION of the amount of GENETIC merit that an animal will pass on to its offspring.
EPD example
a bull with an EPD for weaning weight of +25.0 pounds means that the bull's offspring should average 25.0 pounds more at 205 days of age than offspring of a bull with an EPD for weaning weight of 0.0 pounds.
EPD Abbreviations
BW = Birth Weight WW = Weaning Weight (205 days of
age) YW = Yearling Weight (365 days of
age) milk = maternal milking ability
expressed in pounds of calf weaned.