Download Genetics - mbatts2khs

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
 Observable PHYSICAL
characteristic
GENOTYPE
Phenotype=Black
Genotype=BB or Bb

An organism’s GENETIC
code (genes)
(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
Quarter Horse
Chihuahua
Clydesdale
Australian
Shepard
Arabian
Terms in Genetics

Purebred
 Individuals within a BREED
 Must have all of the required
CHARACTERISTICS
 Recorded PEDIGREE
Terms in Genetics

Dominant alleles
 Represented 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
b
B
Holstein Cattle
• Black & White
Bb
b
Bb
bb
Bb
bb
• Red & White
bb
b
Your Turn!

Solve the genetic problems using a
Punnet Square
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:
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

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!!!
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
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

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
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
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!
