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.