AB EXAM 1

What's the most important Trait

Fertility

What helps measure the “Best animal”

Traits

Whats the goal of breeding

To produce acceptable offspring

Paternal Traits

Griwth amd Size

Maternal Traits

Carcass quality, milk, mothering

Black faced sheep are more

Paternal

Meat breeds are also referred to as

Terminal breeds or sire breeds or paternal breeds

There are no bad traits only bad

Performances

What's the #1 registered breed

Brangus

Trait

An observable or measurable characteristic of an individual

Scurs

Horns not attached to the skull

Phenotype

Observed category or measure of performance for a trait of an individual

P = G + E

First P =

Biological type

Similar genotypes for traits of interest (ex. Meat types and wool types)

G x E Interaction

Difference in performance between two or more genotype changes from environment to environment, must include 2 genotypes and 2 phenotypes at minimum

What are the two types of GxE interactions

Change in Rank (x vs parallel) and change in magnitude (angle change or same)

What jurisdicts the genotype

The environment

Breed

A race of animals within species

Population

A group of intermating individuals (herd, flock, species, etc.)

Selection

Which animals become parents

Natural Selection

Selection independent of humans

Artificial Selection

Human controlled selection

Performance

Measure trait and see if they're good or bad for the trait

What values do you look for when selecting the “best” breeding value

Performance, information on relatives, progeny, and genomic information

Polygenic traits

Many genes influencing the trait (ex. Hip height)

Simply Inherited Traits

Few genes influencing the trait (ex. Color)

Mating systems

Putting genes together for systems, trying to get “the best of both worlds”

What can be bred together

Lines, breeds, and species

The goal of breeding is to

Try to keep lines of animals with the genes you want

Corrective mating

Mating to correct a problem

Linebreeding

Mating related individuals

Quantitative traits =

Polygenic traits

Where is the central tendency

Middle of the chart

A bell shaped curve includes

All of the population phenotypes for one trait

Normal Distribution

Affected by many genes at many levels

Extremes

Furthest from the mean

Population mean symbol

μ

Sample Mean symbol

x̄

Sample Size symbol

N

Mean

Arithmetic average

Sample mean

Sum of all observations

Variation

How individuals vary for a particular trait in a population

Variance symbol

σ²

Standard Deviation

A mathematical measure of variation that can be though of as an average deviation from the mean.

Standard deviation symbol

σ

What does the “^” hat mean

Estimate

σ equals

68%

σ + 2 equals

95%

σ + 3 equals

99%

Correlation equation

cov(X,Y) / (σx)(σy)

Regression

The amount of change in a variable that can be expected for a given amount of change in another variable (cause and effect) (if one thing changes how does it effect the other)

Estimate of Vairance equation

σ²x = Σ(xi- μx)² / n-1

Regression equation

bxy = cov(X,Y) / σ²y

P = μ+BV+GCV+E

Second P equation

Prediction equation

Yi = my + byx ( xi- μx )

Covariance equation

cov(X,Y) = Σ ( xi - μx ) ( yi - μy ) / n - 1

Performance isn't inherited, what is

The gene that controls performance

Gene / Allelic Frequency

Frequency of a gene in a population

p is

The frequency of the dominant gene

q is

The frequency of the recessive gene

p + q =

1

p = (gene frequency)

2 (dominant, homozygous ex. BB) + H / Total

q = (gene frequency)

2 (recessive, homozygous ex. bb) + H / Total

p + q + r =

1

P

Genotypic frequency for homozygous dominant genotype

H

Genotypic frequency for heterozygous genotype

Q

Genotypic frequency for homzygous recessive genotype

P + H + Q =

1

What are the effects of selection

Increase frequency of favorable genes and the genotyoes catch up

Fixation

Selecting until there's one gene in the population (ex. p=1 or q=1)

What are the effects of mating systems

Inbreeding and outbreeding

Inbreeding

Increase homozygosity, decrease heterozygosity (common ancestors)

Outbreeding

Increase heterozygosity, decrease homozygosity (mating to unrelated individuals)

Hardy Weinburg Equilibrium

p² + 2pq + q² = 1

p =

P + ½H

q =

Q + ½H

Q =

q²

P =

p½

Threshold Traits

Polygenic trait that exihibits categorical phenotypes ( ex. Dystocia and fertility)

What do mating systems create

Gene combinations

Factors influencing effectiveness of selection (rate of change)

Initial gene frequency, fitness, and degree of dominance

No dominance

Fastest change occurs at intermediate gene frequency, less desirable eliminated quickly

Complete dominance

Select against dominant allele, few recessive apparent, slow then fast

Recessive

Select against recessive hide in heterozygotes and resistant to selection, fast until recessive allele becomes rare

Why do we see so many recessive genes for true genetic defects despite strong natural and artificial selection against them?

Can't see most genetic defects and carriers look normal but come in with the genes.

When is a genetic model used

Quantitative traits

You can have an average breeding value for

A certain population

Basic genetic model for quantitative traits

P = μ + G + E

Breeding value

The sum of independent gene effects of the animals genes for a particular trait

How much of BV is transmitted

Half from each parent

What is EBV

Estimated breeding value

If theres no dominance then

BV = G

PD =

½BV

Another name for BV

Additive values

Polymorphism

Difference or variance in genes

Gene Combination Value (GCV)

Remaining portion of that value for a trait due to gene combination effects

GCV =

Dominance + Epistasis

G =

BV + GCV

New model with GCV

P = μ + BV + GCV + E

Repeated Traits

Traits for which individuals commonly have more than on performance record