Animal breeding terminology Flashcards
Trait
Any observable or measurable characteristic of an individual.
For example
Observable trait - coat colour Measurable trait – lactation yield
Qualitative traits
– A trait in which phenotypes are expressed in categories (“Either/Or”)
– Are affected by one or at most a very few genes
– Examples
• Polled vs. horned condition
• Coat color in Angus (black vs. red)
• Coat color in Shorthorns (red, roan, or white)
– A trait in which phenotypes show
continuous (numerical) expression
– Polygenic control - many genes, each having a relatively small contribution to the genetic merit of the animal.
– e.g. height, weight, milk production, backfat thickness, etc.
– Exception - A major gene
Phenotype
– Is the appearance or observed performance for a trait in an animal.
– An animal has a phenotype for coat color (e.g., black vs. red).
– An animal has a phenotype for weight
– A dairy cow has a phenotype for milk production
Genotype
– Is the animal’s genetic makeup.
– A genotype is the combination of genes at a single locus or at a number of loci.
– For example, an Angus cow or bull has a genotype for coat color (BB, Bb, or bb).
– An animal also has a genotype for weight, milk production, etc, which consists of all the genes that influence that particular trait.
What is the Dominant phenotype for Angus cow
Black(BB,Bb), red (bb) are recessive
Simply-inherited Trait
– A trait only affected by a few genes e.g. horned/polled
Polygenic Trait
A trait affected by many
genes, no single gene having an overriding influence e.g. weaning weight in sheep, fertility in mammals, conformation and personality in dogs, and growth rate in cattle.
Germ Plasm
The genetic material in the form of live animals, semen, or embryos.
Seedstock
Breeding stock, animals whose role is to be a parent to contribute genes to next generation
Purebred
Wholly of one breed or line
Population
A group of intermating animals. The
term may refer to a breed, a herd or an entire species
Line
A group of related animals with in a breed.
Breeding Value
The value of an animal as a (genetic) parent.
Heritability
A measure of the
strength of the relationship between breeding values and phenotypic values for a trait in a population.
Genetic Prediction
Area of animal breeding
concerned with measurement of data, statistical procedures, and computational techniques for predicting breeding
Sire Summary
A list of genetic predictions,
accuracy values and other useful information about sires in a breed.
Progeny data
Information on the genotype or performance of descendants of an individual
Major Gene
- A gene that has a major influence on a quantitative trait
- Quantitative traits, while mostly influenced by many genes, each having a small effect, in some cases are also influenced by major genes
Double muscling gene
– Cattle with this gene are extremely heavily muscled.
– Double muscling is due to a mutation in the myostatin or growth and differentiation factor (GDF-8) gene
– Mutations render the gene inactive, and therefore, unable to regulate muscle fibre deposition
– Penotype occurs at a high frequency in some breeds of cattle
• Belgian Blue and Peidmontese.
Callipyge gene
– A gene found in sheep that results in a condition similar to double muscling in cattle.
– “Callipyge” comes from the Greek words for “beautiful buttocks”.
– Sheep with this gene have extreme muscling in their loins and hind legs.
• The gene greatly increases muscling and decreases fat.
Halothane gene (stress gene)
– Called so because of the adverse effect of halothane anaesthetic on pigs carrying this gene
– Found primarily in the Pietran breed and Pietran crossbreds with a low frequency in most breeds
– Causes reduced litter size, reduced growth rate, and reduced carcass length
– Also causes increased loin eye area and increased lean%
– Biggest disadvantage is that it causes PSE
• Pigs with this gene are susceptible to stress and tend to have PSE (pale, soft, exudative) pork.
Rendement Napole (RN-) Gene
- Appears to be dominant
- Found primarily in purebred or crossbred Hampshire populations – “Hampshire effect” or “Acid meat”
- Negative effects on meat pH, water holding capacity, color, drip loss, cooking loss, and processing yield
Variation of Quantitative Characters
- Variation is defined as the observable difference between individuals
- We want to identify sources of variation in animals and separate the variation into its component parts
What can Phenotypic variation can be separated into
– Genetic causes
– Environmental causes
What can Genetic causes of variation be subdivided into
– Additive components
– Non additive components
What does non additive gene caused by
interactions among genes
– Dominance is due to interactions between alleles at the same locus
– Epistasis is due to interactions between genes at different loci
• Environmental causes of variation
– Diet – Weather – Health program – Facilities – Management practices
Hereditary Causes of Variation
• Differences in genotypes of individuals cause genotypic variation, which in turn causes phenotypic variation
• Genotype of an individual is fixed at conception and stays the same until death
• Genotype of an individual is determined by the parents
– One-half of the genes come from each parent
• No two individuals have the same genotype (unless identical twins or clones)
Are Qualitative traits influenced by environment
No
Are Quantitative traits influenced by environment
Yes
– Even for a highly heritable trait, a large amount of the phenotypic variation is due to the environment
– h2 of post-weaning gain in cattle = 0.55 or 55%
• 45% of the variation in post-weaning gain is due to the environment, even though post-weaning gain is a highly heritable trait
Booroola (FecB) Merino gene
– Found in a strain of Merino sheep
– Booroola = mutation in BMP1B receptor gene
– (bone morphogenic protein receptor gene
– oocyte & ovary granulosa cells)
– Lack of signal to limit ovulation to one follicle
– This gene increases the ovulation rate and number of lambs born in sheep.
• Average number of lambs born per ewe lambing = 2.4 (range = 1 to 6 lambs)
• Litter size in heterozygous ewes is increased by about 0.9 lambs.
Double muscling gene
– Cattle with this gene are extremely heavily muscled.
– Double muscling is due to a mutation in the myostatin or growth and differentiation factor (GDF-8) gene
– Mutations render the gene inactive, and therefore, unable to regulate muscle fibre deposition
– Penotype occurs at a high frequency in some breeds of cattle
• Belgian Blue and Peidmontese.
Callipyge gene
– A gene found in sheep that results in a condition similar to double muscling in cattle.
– “Callipyge” comes from the Greek words for “beautiful
buttocks”.
– Sheep with this gene have extreme muscling in their
loins and hind legs.
• The gene greatly increases muscling and decreases fat.
Halothane gene (stress gene)
– Called so because of the adverse effect of halothane
anaesthetic on pigs carrying this gene
– Found primarily in the Pietran breed and Pietran crossbreds with a low frequency in most
breeds
– Causes reduced litter size, reduced growth rate, and reduced carcass length
– Also causes increased loin eye area and increased lean%
– Biggest disadvantage is that it causes PSE
• Pigs with this gene are susceptible to stress and tend to have PSE (pale, soft, exudative) pork.
Rendement Napole (RN-) Gene
• Appears to be dominant
• Found primarily in purebred or crossbred Hampshire
populations – “Hampshire effect” or “Acid meat”
• Negative effects on meat pH, water holding capacity,
color, drip loss, cooking loss, and processing yield
Permanent Environmental Effects
Are environmental effects that stay the same from one record to the next on an animal
– Stay with animal throughout its lifetime
– If a cow loses function of one quarter of her udder due to injury, it will influence her milk production in all future lactations
• The feeding program used to raise heifers, if extreme
(e.g., too much feed or not enough feed) can influence
mammary gland development, which becomes a
permanent environmental effect
– Will influence all future lactations
Temporary Environmental Effects
• Are environmental effects that change from one record to the next on an animal
– Cold and snowy winter one year vs. mild winter the next year
– Drought one summer vs. normal rainfall the next summer
