Animal Breeding Exam 2

Assumption for Equilibrium

Random mating, large population, equal fitness and fertility among genotypes, equal gen frequency between sexes

True/False

Domestic animals follow the assumption for equilibrium

False; their populations are heavily in influence by human intervention

Equilibrium

a state in which opposing forces or influences are balanced (don't change between generations)

Why is gene frequency important?

A change in gene frequency may change the mean performance of a population.

What are 4 ways to change a gene frequency?

Drift, mutation, migration, selection (DMMS)

Drift (random change)

-Random statistical fluctuation

- independent of natural selection

- sampling nature of inheritance

Mutation

-biochemical event of a change in DNA sequence

-source of all variation on an evolutionary scale

Migration

- a mixture of populations similar to what often occurred in herds

-bringing in new genetics from outside of the population

-potential to make rapid changes in gene frequencies

selection

-choosing those animals with a high number of desired alleles from the population

-can be 2 types: natural and artificial

artificial selection

Selection by humans for breeding of useful traits

natural selection

Selection that is done by nature in causing the death of the less viable individuals or lower reproduction rates

True/False

Once you switch your population you must use other forces to effect further change.

True

Novel genes

genes that are unique to a species

bottleneck effect

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.

Ne

Effective number of breeding animals

Is the fact that domestic populations are not in H-W equilibrium good or bad?

-Bad

-loss of genetic diversity, increased risk of genetic disorders, loss of traits used in the wild

- Pparent=POffspring=no change

Genotype frequency

p+q=1 and p2+2pq+q2=1

P=

frequency of dominant allele

Q=

frequency of recessive allele

N

Total number of events

S

Total number of times events a occurs

T

Number of times event b occurs

A

Chance of event a occurring each time

B

Chance of event b occurring each time

Probability

-likelihood that a particular event will occur

- P= n!/s!t! (a^s•b^t)

Quantitative Traits

-Must be defined numerically to be accurately described, continuous variation

Ex: Feed efficiency, growth rate, speed, milk yield, fat content, agility

Qualitative Traits

-don't need metric definition to be accurately described

-discrete variation

Ex: Horns, colors, Cleft palate, PSS, rate of feathering

Accuracy

-correlation between the estimated and true genotype

-Degree of success in selecting for traits depends on courtesy of estimate

-least accurate due to "fuzzy" observation

Ex: large grouping of arrows on bullseye

Accuracy Genotype

Cumulative effect of all loci

Loci

Location of a gene on a chromosome

incomplete dominance

-Dominant allele does not dominate the recessive allele entirely

-intermediate trait appears in the offspring

Ex: Pink flower with red and white parents

Co-Doninance

When the alleles do not show any dominant and recessive allele relationship

Ex: a flower with white and red alternating

Dominance

-A characteristic in which an allele that expresses its phenotype even in the presence of a recessive allele

Ex: RR= Red

Recessive

-An allele that is masked when a dominant allele is present or expressed without a dominant allele

Ex: Bb or bb

Homozygous

Having two identical alleles for a particular gene

Heterozygous

having two different alleles for a particular gene

Heritability (h2)

-Portion of the phenotypic variance in a population that is due to heredity

Heritability estimates

-indicate the portion of an individual phenotypic superiority or inferiority to transmit to its offspring

- %heritability= variation due to heredity/ variation due to both heredity and environment X 100

-Low heritability: h2<0.20

•survival and Reproductive traits, such as disease distance, litter size, calving interval, longevity in herd

• see more results from managing the environment, rather than selecting for those traits genetically

Moderate Heritability: 0.20

• growth and production traits like weaning weight, average daily gain, milk, yield, birth weight

• pay to select for these traits and manage the environment because these are often the traits you get paid for

High Heritability: h2>0.40

• structural traits in qualitative traits, such as bone, fat, mature size, color, horns

• easy to make fast selection progress because they are not influence much by the environment. However, they may not be terribly valuable in a production setting.

General Heritability Trends

Low heritability, moderate heritability, high heritability

Estimated breeding individual

EBV= h^2 (Pi-Pherd)

Pi

Average performance of individual

Pherd

Average performance of herd

n

Number of records for an individual set of data

R

Repeatability of the trait ratio (typically given)

MPPA

= Pi + nR/[1+(n-1)R] (Pi-Pherd)

Trait Ratio

= Pi/Pherd • 100

True/False

Selection differential can be accumulated over multiple generations

True

Repeatability Estimates

Likelihood that individual will tend to repeat records for a particular trait throughout its life

Ex: milk production at different times in the life of the same individual

Most Probably Producing Ability (MPPA)

is an estimate of producing ability; is a prediction of the next record

True/False

Heritability and repeatability are both average figures and may not be exact for a specific individual or herd

True

Pedigree

A record of an individuals ancestors related to it through its parents

True/False

Data to indicate phenotypic merit of ancestors have ALWAYS been included in "performance pedigrees"

False; they are just now starting to be included

What factors influence the value of performance records of an ancestor?

-the degree of relationship between the ancestor and the individual

-the degree of heritability of the trait

-environmental correlation among animals used in the prediction

-how completely the merit of the ancestors use in the prediction is known

Selection on the basis

The breeder makes a decision to keep or call a sir or dam, based on the average merit of their offspring as compared to the average merit of the prodigy of contemporary sires and dams

True/False

The most effective use of prodigy test and selection for quality traits is to determine if an individual of the dominant phenotype is homozygous or heterozygous.

True

To produce a pure breeding line for a dominant trait what has to happen?

All homozygous, recessive, individuals, and heterozygous and individuals must be removed

True/False

It's much harder to progeny test for recessive genes in litter-bearing individuals

False; it's much simpler

What is the principle involved in the progeny test?

Each progeny receives 1/2 of its inheritance from each parent, and this is a sample 1/2 of each parents breeding value

True/False

The more closely they are related to the individual in question, the more valuable is the information they can apply for selection purposes

True

What does the selection on the basis of sibling test mean?

An individual is kept or cold for breeding based on the average phenotype of its brothers and sisters

Relationships

-parents you offspring R= 0.50

-grandparent to grand-offspring R=0.25

Full Sibling R=0.50

Half Sibling R=0.25

/\P=

Heritability*Selection Differential

Selection differential

Difference between meaning of selected parents, and the population from which they came

How do I increase selection response per year?

-select a trait with a higher hair ability and/or increase variation

-increase accuracy

-increase select intensity

-decrease generation interval

Miniature Horse

-Origin: Northern Europe

-miniature horse

-Stand a max of 34" at the withers

-Dwarfism

-any color

- pets/ pulling carts in mines

Shetland Pony

-origin Shetland island (Scotland)

-Pony

-oldest and smallest of the pony bred

-often sorrels but can be any color

-showing, harness racing and children mounts

Pony of America

-Origin Iowa

-Pony

-cross between Appaloosa and Shetland pony

-any color with Appaloosa type pattering

-Pleasure, horses, and young rides

Stand between 46"- 56"

Welsh Pony

-Origin Wales

-pony

-Thoroughbred and Arabian influence

-coat is commonly black or gray, but can be bay, gray, chestnut

-12 hands

-Red coal mining but now popular for children and small adults

Arabian

-Origin Arabia

-foundational light

-colors are often bay, gray, chestnut, black

-14-15 hands

-Riding horse for endurance

- dished face, high head and tail carriage

- "Father breed" of light horses

Thoroughbred

-Origin, England

-foundational light

-coat colors bay, gray, chestnut, black

-15-16 hands top

-light breed if riding horses known for speed over intermediate distances

-race horses, and speed and horses

Quarter horse

-origin, USA

-light horse

-coat colors, all colors without excessive white

-14-16 hands tall

- light breed of horses and known for speed over short distances

-stock horses, all around horses, rodeo horses, short distance, race horses

Standardbred

-Origin eastern United States

-light horse

-coat colors bay, brown, chestnut, black, gray, roan, fun

-15-16 hands tall

-known as trotters and pacers, these horses are not ridden, but used for harness racing and showing

Morgan

-Origin, United States of America, New England

-light horse

-color colors bay, black, brown, or chestnut

-14-16 hands tall

-known for using temperament, docility, and longevity

-used for stock, saddle, and harness horses

American paint

-Origin, United States of America

-light horse

-originated from quarter horse and thoroughbred conformed horses (other breed types fall into pintos)

-coat colors any base color with white pattern, distinct pattern including Tobiano and overo

-14.2-16.2 hands tall

-stock, pleasure, racing and showing

American Saddlebred

-origin USA

-light horse

- coat colors bay, black, brown, chestnut, gray

-15-16 hands tall

-Head and tail high carriage

- 3 gaits or five gaited horses move with much action and high, stepping, docile and intelligent, have endurance and improve easy writing on rough terrain

-used for pleasure, stock and fine harness horses

Clydesdale

-origin Scotland

- Draft

- bay, brown, or black with white markings, leg feathering is straight silky and heavy

-used for cart pulling and working land

Belgian

-origin Belgium

-draft

-bay chestnut or sorrel

- thicker, curlier hair BUT NOT FEATHERING

- used for cart pulling and working land

Shire

-origin England

-draft

- bat, brown, or black with white markings, feathering is straight, silky, and heavy, neck is long and shoulders are wide and deep

- more athletic, largest of the modern horse, used for pulling carts and working land

Percheron

-origin France

-draft

- dapple gray or black most common but as bay, brown, chestnut or roan

-head is attractive and clean cut, legs have no feathering, good temper

- used for battle, farming and pleasure riding

Trakehner

-origin Trakehnen, east Prussia

-warm blood

-bay, gray, chestnut, or black, bred to be big and more powerful but also athletic

- used for equestrian activities

Holsteiner

-origin Germany

- warm blooded

-bay, gray, chestnut or black

- equestrian sports

Hanoverian

-origin Germany

- warm blood

- most conformational balanced, original carriage horse but now used in English equestrian sports