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Summary ABG-20306 - Animal Breeding & Genetics
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Korte samenvatting over H1-14 van Animal Breeding and Genetics.
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Summary ABG-20306Chapter 1
Animal breeding: selective breeding of domestic animals with the intention to improve desirable
qualities in the next generation.
- To maintain genetic diversity
- To improve a genetic level of a population
Trait: a distinguish phenotypic characteristic, typically belonging to an individual. It is everything you
can measure and record. Traits are heritable. F.e. milk yield/litter size/ speed/ height
How can you get genetic improvement?
- Artificial selection of the best animals
- Next generation better than the current one
- Improvement across generations is cumulative
Inbreeding: mating of relatives
- Loss of genetic variation and loss of genetic diversity
- Inbreeding depression
- More homozygosity
- More recessive diseases
Crossbreeding:
- Hybrid vigour/heterosis
- Is doing better than average of parents
Breed: group of animals of a certain species that through generation of selective breeding has
become uniform in performance, appearance and selection history.
Species: largest group of animals that are able of interbreeding and producing fertile offspring
Phenotype: what you observe or measure on the animal for a certain trait. It can depend on:
- Genetic background
- External circumstances
The first domesticated animal was the dog, then the sheep, pig, goat, cattle, cat, chicken, etc.
Chapter 2
Production system = circumstances
- Geographic location
- Purpose of animal (production/sport/working/saving)
- Animal species and breed
Breeding goal:
- Combination of specific traits
- Specifies which traits should be improved, in which direction and relative emphasis given to
each trait
- Economic/non-economic
, o Economic value: expected net profit of improving a trait with 1 unit
- F.e. increased milk yield/life span/fertility/egg production/trainability
- Breeding goal Holstein:
o H = breeding goal
o v = value trait
o A = breeding value
o Consists of a combination of traits
o Should summarize all traits in a single criterion
o Contains breeding values and economic values
o Should aim at the future
o May contain economic and non-economic weights
Breeding program:
1. Definition of production system
- The production system and the markets define the traits for the breeding goal
2. Definition of breeding goal
- Sets the desired direction of change
3. Collection of information
- Phenotype (we need the value of trait of interest)
- Family relationships (used to estimate the genetic potential of candidates for the trait of
interest)
- Genotypes
4. Determining selection criteria
- Estimation of breeding value (estimation of the genetic potential of an animal for a given
trait)
- Genetic models (estimate amount of variation) -> used to estimate breeding values
5. Selection and mating
- High selection intensity: only the best parents are used for selection
- Predicting selection response
6. Dissemination
- Breeders -> breeding companies – pure line breeding
- Multipliers -> multiplying animals + crossbreeding
- Producers -> commercial farms: production animals
, 7. Evaluation
- Selection response (revenue)
- Costs
- Inbreeding and genetic diversity
- Improvement of genetics
Chapter 3
Gamete: haploid -> contain only a single allele at each locus
Allele: sequence of DNA nucleotides at a locus (locus = position on a chromosome).
- Co-dominance: the phenotypic effects of both alleles are equally shown
- Overdominance: when the heterozygote has a genotypic value more extreme than either
homozygote
- Incomplete dominance: that the heterozygote is not exactly in the middle
- Epistasis: when he effects of separate loci are non-additive
o Between alleles at different locus
Correlation coefficient (r)
- Measures how accurate two random variables are related
Regression coefficient (b)
- Measures the relationship between the level of two random variables
Chapter 4
Pedigree: set of known parent-offspring relationships in a population
- Information of relatives to estimate breeding values
- Avoid mating close relatives
Traits
- Quantitative traits
o Polygenic: influenced by effects of many genes
o F.e. length, weight, amount of offspring
o Can be expressed in a number
- Qualitative traits
o Limited number of genes are involved
o F.e. eye colour, gender
Collect DNA
- Blood collection
- Mouth swab
- Hair roots
Genetic marker: part of a DNA sequence that has a known location.
- Microsatellite: repeat in sequence
- Single nucleotide polymorphism (SNP): location on the genome where a single base is
replaced by another one -> point mutation
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