GENETICS

Obj: Discuss reproductive management terms used in the animal science industry.

Natural Selection

No human intervention Survival of the fittest Based on an organism’s ability to

SURVIVE and pass on its GENETIC information to its offspring

Artificial Selection

HUMANS control which organisms pass their GENETIC information (reproduce)

Phenotype VS. Genotype PHENOTYPE GENOTYPE

Observable PHYSICAL characteristic

Phenotype=Black

An organism’s GENETIC code (genes)

Genotype=BB or Bb (Pattern of letters representing the genes for color)

Terms in Genetics

Genes: Factor that control traits Alleles: Different forms of genes

Paired (AA or Aa) & represented by a letter

Terms in Genetics

Adaptability: The ability of a BREED to become SUITABLE to conditions

Terms in Genetics

Type: a group of ANIMALS that are grouped together according to the PRODUCTS they produce Examples: Beef type cattle, Dairy type

cattle,

Terms in Genetics Species: a group of similar organisms

that can produce fertile offspring

Canine Equine

Terms in Genetics Breed: animals having a common ORIGIN

and CHARACTERISTICS different from animals within the same SPECIES

Labrador

Chihuahua

Australian Shepard

Quarter Horse

Clydesdale

Arabian

Terms in Genetics

PurebredIndividuals within a BREED Must have all of the required

CHARACTERISTICS Recorded PEDIGREE

Terms in Genetics

Dominant allelesRepresented by capital letters This trait is the one expressed

Recessive alleles Represented in lower case letters Only expressed if both parents donate

recessive genes for a trait

Terms in Genetics

Homozygous: Alleles express the same trait type (BB dominate) OR (bb recessive)

Heterozygous: Two different alleles for the same trait (Bb)

Punnet Square

A method of calculating the chances of inheriting a specific trait

Bb bb

Bb bb

B b

b

b

Holstein Cattle

• Black & WhiteBb

• Red & Whitebb

Your Turn!

Solve the genetic problems using a Punnet Square

Breeding Systems

Breeding Systems

How to design a breeding system:

1. Set Goals

2. Choose measurable traits

3. Select parents according to goals

Breeding Systems

Traits to breed for:

MILK

# BORN ALIVE

Coat ColorHeight

Birth WeightSpeed IndexWeaning weight

Breeding Systems

How to measure traits Qualitative Traits

Controlled by SINGLE pair of genes Not altered by environment Example: Coat Color

Quantitative Traits Controlled by SEVERAL pair of genes Can be altered by environment Examples: Weight gain, growth rate, backfat

depth, etc.

Breeding Systems

Breed only animals that are purebred with registration papers

Goal: To produce high quality animals to sell as breeding stock

Purebred

Breeding Systems

Breed purebred sires to commercial females Replacement females are kept and bred

back to the purebred sire GOAL: To produce progeny resembling the

purebred sire and SAVE $$

Most common in the livestock industry!!!

Grading Up

Breeding Systems

The mating of animals of different breeds GOAL: To take advantage of hybrid vigor

and hopefully have offspring inherit good traits of both parents

Hybrid vigor: crossbred offspring exceeds the average of the two parental breeds

Crossbreeding

Breeding Systems

Mating of related individuals- sires and dams that share at least one ancestor

Necessary when creating new breeds or when you need to isolate genes for chosen traits

GOAL: Isolate unique/rare genes and perpetuate them

Inbreeding

Breeding Systems

Increase uniformity of offspring Could result in the surfacing of deleterious

genes Reduction in performance because what use to

be hidden by recessive genes is now expressed

Deleterious gene: Could cause undesirable effects on an individual’s viability, productivity and/or economic value

Inbreeding

Examples of Deleterious Genes

“Lethal White” gene in Paints: Foals carried full term All white or mostly white coats Look & seem fine at birth BUT colon is non functioning.

They show symptoms of colic and die within 48 hours.

Gene is carried on the overo color gene

Recessive gene was perpetuated as overo paints were bred

Breeding Systems

A minor form of inbreeding with the attempt to keep a relationship to a highly regarded ancestor

Elite Sire X Half Sisters

Son of Elite Sire X Daughter of above Females

Grandsire X Granddaughters

Line Breeding

Create Your Own Breed

Every breed of animal that we are familiar with today was once developed through generations of selective breeding to isolate specific traits unique to the breed.

You will now choose traits you like in a certain species to create you own new breed!