425667
Description
Flashcards by Sophie Mae Neash, updated more than 1 year ago
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Created by Sophie Mae Neash
over 10 years ago
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| Question | Answer |
| What is the aim of selection? | To breed from animals who will produce the best progeny |
| What three things increase the rate of genetic gain? | 1) a high phenotypic variation 2) a high heritability 3) A low proportion of selected animals |
| Why do we want a high phenotypic variation? | So the selected animals have the potential to be better than the average. |
| Why do we need a high heritability? | So the superiority of the parents is passed on to the offspring |
| Why do we want a low proportion of selected animals? | So selection differential is high and so selection intensity is high |
| What is the generation interval? | The average age of the parents when the offspring are born |
| How do we calculate the generation interval? | Average of the parents in the herd / 2 |
| Why do we divide the number by 2? | As the progeny gets half their genes from the dam and half from the sire. |
| What is the response to selection? | The mean performance of the progeny minus the mean performance of the parent generation |
| What does response to selection depend on? | Heritability (h2) and superiority (s) |
| How is superiority determined? | The mean of selected animals - the mean of the whole population |
| How is response to selection calculated normally? | R = h2 x S |
| How do we maximize response to selection per year? 4 things | 1) low generation interval 2) high phenotypic variation 3) high heritability 4) High selection intensity |
| How do we determine response per year? | R = i x h2 x SD / L or R = s x h2 / L |
| What is the selection intensity? | The number of standard deviations that the animals are superior to the mean |
| How do we determine si? | Si = i x SD |
| What is selection differential (intensity) determined by? | The proportion selected (p) and the standard deviation |
| How does standard deviation affect selection differential? | As standard deviation increases, selection differential increases |
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