Genetic decision making in animal breeding Flashcards
What are the pressures when making a decision about animal breeding?
availability of information
financial and physical resources
current breeds in use
local traditions
market demand
personal preferences
Describe a breeding pyramid
What is heterosis/’hybrid vigour’
extra performance of offspring above mid-parent mean
opposite of inbreeding depression
What is the
backcrossing?
the mating of a hybrid organism (offspring of genetically unlike parents) with one of its parents or with an organism genetically similar to the parent
As a result the genotype of the progeny becomes genetically similar to the parent
What methods are there for selecting an animal to breed
Pedigree selection - combines info of ancestors performance
Performance test - selection of animals own performance
Sib pair test - selection based on info from siblings
Progeny test - based on performance of an animals offspring
What is the response to selection?
the change in mean performance in a population of animals as a result of selection - usually per year or generation
Response to selection = selection differential(S) x heritability (h2)
what is generation interval (L)?
average age of an animal when their offspring are born
How do you calculate response to selection per year?
What is inbreeding?
the mating of individuals more closely related than average for the population
what is the ultimate result of inbreeding?
terminal lack of vigour and probable extinction as gene pool contracts, fertility decreases, abnormalities increase and mortality rates rise
What are the practical applications of inbreeding?
breeding of companion animals
Control of inheritable disease
management of zoo populations and endangered species
estimation of heritability
artificial selection programmes
What is the reason for inbreeding?
related animas have more alleles in common
logical to mate related individuals with favourable alleles to increase the frequency
What is the effect of inbreeding?
decreased heterozygous genotypes and increased homozygous genotypes
What is inbreeding depression?
Increased homozygosity => reduced amount of genetic variation in a population => reduced response to selection and can lead to decline in performance in traits associated with fitness e.g., repro rate and disease resistance
opposite of heterosis
Explain genes identical be descent
2 alleles are copies of a single gene inherited from a common ancestor of 2 seemingly unrelated parents of the individual
