Population Genetics Flashcards
How is a breeding value measured?
by PTA (predicted transmitting ability) or EBV (estimated breeding value)
What is the relationship between PTA and EBV?
PTA = 1/2 EBV
What is PIN?
profitable index
Kg of milk, fat and protein
What is PLI?
profitable lifetime index
combined PTA’s weighted differently - milk, fat, protein, lifespan, SCC, locomotion
What is the fertility PTA based on?
calving interval and non-return rate
what does a high calving interval mean?
poor fertility - too long to get back into calf again
what does a high non-return rate mean?
good fertility - most getting pregnant first time of AI
How is robustness PTA measured?
BCS, environmental sensitivity of genes, health, fertility
In small animals what are the 4 genetic forces?
- mutation
- migration / outcrossing
- genetic drift and inbreeding
- selection
What does an inbred individual have?
An inbred indiviual has identical alleles coming from the same ancestor
What is the inbreeding coefficient?
the probability that the 2 copies of the gene are IBD (inherited by descent)
look at probability of inheritance for each allele for each mitotic event
What is the problem with inbreeding depression?
can compromise the fitness of the whole line and make some individuals very sick
what is ∆F?
change in average inbreeding coefficient over time / generation
the change represents a change in diversity
What ∆F is acceptable and why?
less than 0.5% / year - its a decrease in diversity
What is Ne?
effective pop’n size
the number of breeding individuals in a hypothetical random mating pop’n that would have the same rate of inbreeding seen in the real pop’n
What Ne is wanted?
at least 100 for a fit pop’n
What is the relationship between Ne and ∆F?
Ne = 1/2 ∆F
What are solutions to inbreeding?
minimise kinship matings increase no of animals used for breeding equalise use of males and females optimise genetic contribution out-crossing
What is a single gene disease?
1 locus
env’t has no effect
What is a complex disease?
env’t has an affect and is multi genetic
why is genomic EBV better than EBV?
gEBV you can take a swab a few weeks after birth and get accurate results
EBV you dont get accurate results until the animal has offspring to evaluate
What is selection intensity?
the difference between the population mean and the mean of the selected individuals - it is the cutoff selected below which individuals are allowed to breed
tougher threshold = faster response ..may be bottlenecking the pop’n though