Animal Genetics

Natural Selection n an organisms ability to SURVIVE and pass on its GENETIC information to its offspring.

Artificial Selection n HUMAN control over organisms passing on their GENETIC information.

Heredity n the POTENTIAL an organism has to show certain TRAITS due to its GENETIC information

Environment n the EXTERNAL conditions that affect the traits and PERFORMANCE of an animal

Environment vs. Heredity n An organism's traits and performance are a sum total of its ENVIRONMENT acting upon its GENETIC information.

Environment vs. Heredity n Some TRAITS are influenced more by an organism's ENVIRONMENT than by its GENETICS, while others are influenced more by genetics.

Heritability n The percentage that a trait is affected by its genetic information is called HERITABILITY. n A heritability factor of 0.0 means that a trait is influenced very little by genetic information n A heritability factor of 1.0 means that a trait is influenced very little by the environment.

Examples of Heritability n Birth Weight =.40 n Weaning Weight =.30 n Multiple Births = n Dressing Percentage =.60

Adaptability n The ability of a BREED to become SUITABLE to specific environmental conditions

Type n a group of ANIMALS that are grouped together according to the PRODUCTS they produce n Examples -- Beef type cattle, Dairy type cattle, Wool type sheep, Mutton type sheep

Species n a group of ORGANISMS that have several common CHARACTERISTICS that differentiate them from others.

Scientific Names of Species n Cattle: Bos taurus, Bos indicus n Sheep: Ovis aires n Swine: Sui suidae n Horse: Euquis caballus n Chickens: Galus galus

Breed n animals having a common ORIGIN and CHARACTERISTICS that distinguish them from other groups within the same SPECIES.

Purebred n individuals within a BREED. They must have all of the CHARACTERISTICS of the breed and have a recorded PEDIGREE.

Pedigree n a record of an individual's ANCESTRY.

Breeds of Cattle

Angus

Hereford

Charolais

Brahman

Shorthorn

Simmental

Salers

Texas Longhorn

Red Angus

Limousin

Belted Galloway

Beefmaster

Holstein-Friesian

Guernsey

Jersey

Breeds of Sheep

Rambouillet

Columbia

Suffolk

Hampshire

Merino

Dorset

Lincoln

Breeds of Swine

Duroc

Hampshire

Chesterwhite

Yorkshire

Landrace

Production of Sex Cells (Meiosis) n 1. SIMILAR events to mitosis n 2. Occurs ONLY in the TESTES and OVARIES to produce egg and sperm cells. n 3. REDUCES the NUMBER of chromosomes to half the normal number. n 4. ONE replication followed by TWO cell divisions.

Meiosis

FERTILIZATION n the union of the egg and sperm nuclei n restores the normal chromosome number.

ZYGOTE n a fertilized egg

SPERMATOGENESIS n 1. occurs in TESTES n 2. EQUALLY sized cells n 3. FOUR sperm cells produced

Spermatogenesis

OOGENESIS n 1. occurs in OVARIES n 2. DIFFERENT sized cells n 3. ONE egg cell produced and three POLAR bodies

Oogenesis

Patterns of Inheritance

DOMINANT n the trait that SHOWS in a cross between twotrue-breeding parents n Example in Cattle -- Black coat color, polled n Example in Sheep -- White wool n Example in Swine -- Black hair

Recessive n the trait that is HIDDEN in a cross between two individuals. n Example in Cattle -- Red coat color, horns, dwarfism n Example in Sheep -- Black wool n Example in Swine -- Red hair

PHENOTYPE n the OUTWARD appearance of the organism

Genotype n the actual GENE MAKEUP of an organism

Homozygous n when both of the genes (letters) in the pair are the SAME n Example -- TT or tt

Heterozygous n when both of the genes (letters) in the pair are DIFFERENT n Example -- Tt

Incomplete Dominance n The genes are neither dominant nor recessive, but are equals n Example -- Shorthorn Cattle –WW=White –RR=Red, –RW=Roan

Types of Mating Systems n Purebred n Inbreeding n Linebreeding n Outcrossing n Grading up n Crossbreeding

Hybrid vigor n increased performance of offspring over that of the parents when unrelated individuals are mated. n Heterosis

Performance Pedigrees n summarizes a particular animal's own performance records as well as records of ancestors, siblings, and progeny. n Progeny = offspring

EPD n EXPECTED PROGENY DIFFERENCE n an INDICATION of the amount of GENETIC merit that an animal will pass on to its offspring.

EPD example n a bull with an EPD for weaning weight of 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 n BW = Birth Weight n WW = Weaning Weight (205 days of age) n YW = Yearling Weight (365 days of age) n milk = maternal milking ability expressed in pounds of calf weaned.