Mating Systems and Inbreeding Flashcards
Mating Systems (Overview)
Brings about population improvement
Random vs Non-random
Random Mating System
Hardy-Weinberg can work
Genotypic frequencies dependent upon allelic frequencies
No attempt from breeder to pair specific mates
Non-Random Mating Systems
Strategies for genetic change (2)
Expected proportion of homozygous and heterozygous individuals deviate from HW expectations
Two Genetic Change Strategies
Selection and Mating Systems
Selection
Decide which individuals to retain as parents and which genes will be passed to subsequent generations
Goal of Selection
Higher frequencies of alleles with desired affect and lower freq. of alleles with undesirable affect
Mating Systems (In relation to genetic strategies)
Which males mate with which females
No further changes in allelic freq. beyond selection
But is does alter genotypic frequencies
Non-Random Mating
Assignment of mates based on Genetic relationship and Phenotypic similarities
Genetic relationship
Based on pedigree
Not randomly selected
Males and females mated together: more close relation -> inbreeding
less close relation -> outbreeding
Inbreeding
minimized as much as possible
Attempt to make individuals more homozygous for a gene from common ancestor
Inbreeding coefficient
Probability that 2 alleles at a locus in an individual are identical by decent (coming from ancestor)
Represented by [Fx]
Outbreeding
Increase heterozygosity
Hybrid vigor
Used in meat animal production a lot
Phenotypic similarity
Based on performance
Mate males with females because:
Positive assortative mating and negative assortative mating
Positive assortative mating
Resemble one another more closely
Negative assortative mating
Resemble one another less closely
Correlations between topics
(for mating systems)
Inbreeding and positive assortative mating -> increase homozygosity
Outbreeding and negative assortative mating -> increase heterozygosity
Arrow diagrams
Individuals only appear once, but can trace common ancestor to descendants
Flow of genes through time
Common Ancestor
In general - common for more than one individual on arrow diagram/pedigree
Identical by decent
If S and D have a common ancestor and both possess identical copies of A’s gene
And if X inherits both copies from S and D, X would be homozygous for that gene and that gene would be IBD
Linebreeding
Less intense form of inbreeding
Concentration of ancestral traits
Mating individuals within particular line
Effects of inbreeding
- Prepotency
- Expression of deleterious recessive traits
- Inbreeding depression
- Tends to “fix” traits in population
- Concentrate genes
- Increasing probability of getting similiar genes to offspring from ancestor
Prepotency
Performance of offspring is especially like that of the parent
Attempt to make individuals more homozygous for superior genes
Expression of deleterious recessive traits
Gives inbreeding a bad reputation
Does not create deleterious recessive traits but can expose them
Inbreeding Depression
decline in performance (such as fertility or survival)
Deals with Qualitative traits/Polygenetic traits
Unfavorable gene combination value
Tend to “fix” traits in a population
Becomes identifiable
Concentrates genes
Can be good or bad
