Download ANSC 340 CERTIFICATION EVALUATION GUIDE 2026 FULL SOLUTION and more Exams Reasoning in PDF only on Docsity!
ANSC 340 CERTIFICATION EVALUATION GUIDE
2026 FULL SOLUTION
โ a selection index allows you to look at one or more traits and derive a comprehensive ___ for an animal Answer: BV โ Because a litter is raised by one dam, often the performance of littermates will be more alike than you would expect given the proportion of genes they have in common. This effect, denoted as (c^2), is known as ___ Answer: common environmental effect โ the average performance of many progeny is a good indication of an individuals _____ Answer: BV โ an EPD based on an animals own data is _______more accurate than one based on a number of his progeny Answer: not always โ T/F: the baseline used to compare birthweight EPDs is a standard reference number used by all beef cattle breed associations Answer: false โ heritability for a litter size is 0.4. When computing the accuracy of an EPD for litter size, h^2 =? Answer: 0.
โ T/F: threshold traits are better selected for directly rather than by a correlated trait Answer: false โ bill uses a selection index based on 3 traits. Ted uses an index based on 6 traits. Whose index provides the greatest overall selection intensity? Answer: Bill โ What are the 2 possible causes for the phenomenon of correlated traits? Answer: pleiotropy and linkage (ex. lack of recombination) โ For birthweight: Bull A: Angus EPD = +2 ACC = 0. Bull B: Charolais EPD = - 2.5 ACC = 0. which is better? Answer: cannot choose with the info given (different breeds so you can't compare them) โ when heritability is ____, a sires own performance data is valuable when estimating his EPD for that trait Answer: high โ given the following equation, one would assume... (delta BV y given x)/t = (r bvx, bvy) (acc of x)(i)(sigma bv y) / L Answer: direct selection for trait x may influence the BV for trait y
โ delta BV/t denotes what? Answer: rate of genetic change over time (response to selection) โ r of BV, BV hat denotes what? Answer: accuracy of selection โ i denotes what? Answer: selection intensity โ sigma BV denotes what? Answer: genetic variation โ L denotes what? Answer: generation interval โ ____ is the difference between the mean selection criterion of those individuals selected to be parents and the average selection criterion of all potential parents Answer: selection intensity โ selection intensity is expressed in ___ Answer: standard deviations โ selection differential = Answer: SCs - SC โ selection intensity = Answer: (SCs - SC) / sigma SC โ T/F: you can look at EPDs instead of individual performance, if the trait has a decent heritability Answer: true
โ ____ when there is a clear line dividing who is selected from who is not Answer: truncation โ if theres truncation selection, you can read "i" from a table, based on the proportion of... Answer: animals saved (p) โ selection intensities for threshold traits are often ___ Answer: small โ the better the performance of a population in a threshold trait, the ___ the selection intensity will be Answer: smaller โ select for related traits which are _____ Answer: continuous โ an example of continuous trait Answer: birth weight โ genetic variation is represented by Answer: sigma BV โ genetic variation tens to be fairly ___ within a population, unless specifically managed Answer: fixed โ can outbreeding/inbreeding affect genetic variation? Answer: yes!
โ List some trade-offs among variables in the key equation Answer: accuracy vs generation interval accuracy vs intensity intensity vs generation interval โ ____ in accuracy of selection is often accompanied by a decrease in selection intensity, and vice versa Answer: an increase โ _____: the rate at which selected replacements replace existing parents Answer: replacement rate โ if intensity (for replacements) is high, replacement rate is ____ Answer: low โ if replacement rate is low, then generation interval is ___ Answer: longer โ if culling rate is high, replacement rate is ___ Answer: high โ replacement females: in non-litter-bearing species, selection intensity is ___ Answer: low
โ T/F: with replacement males, with AI, numbers of males are not a problem Answer: true โ _____: the risk that true breeding values of replacements will be significantly poorer than expected Answer: selection risk โ using more sires will ____ i but also ____ risk Answer: lower, lower โ its more important to select __________ more carefully since they can _________ ________ females Answer: sires;cover many โ ____ allows you to weigh info Answer: the selection index โ I = Answer: "index value" โ bi = Answer: weight factor โ xi = Answer: single piece of phenotypic info โ n = Answer: total # of items of phenotypic info โ phenotypic info can come from what 3 things? Answer: 1. an animals own performance record
โ in cases with littermates with common environmental effects, additional records on full sibs provide ____ Answer: less info โ we account for full sibs providing less info by using a measure of the covariation among relatives caused by a ____ Answer: common environment โ c^2 = Answer: common environmental effects โ when heritability is high, _____ is the most valuable Answer: an animals own record โ when heritability is low, ______ are the most valuable Answer: progeny records โ the average performance of many progeny is a good indication of an individuals ____ Answer: BV โ which species is progeny testing common in? Answer: cattle โ which species is progeny testing not common in? Answer: swine โ _____ is the range within which we expect the true value to lie with a certain level of confidence Answer: confidence range
โ accuracy increases and confidence ranges decrease as records ___ Answer: increase โ ____ heritability means you need more records Answer: low โ EPDs derived from progeny records are very easy to misinterpret without ____ or ____ info Answer: accuracy or CR โ It is very risky ti evaluate a dam with ___ progeny #s, unless looking at a dam ___ Answer: low, trait โ T = Answer: some true value (BV, PD, etc.) โ 68% CR = Answer: EPD (+/-) sqrt((1-acc^2)*variance of PD) โ can use multiple sources of info in the selection index such as from.... Answer: individual, half sib, and progeny โ _____ is a prediction based solely on pedigree data Answer: pedigree estimate โ pedigree estimate ________ reliable Answer: is NOT
โ ____ allow comparison of genetic merit of animals across herds/flocks Answer: large-scale evaluations โ what are 3 things you can do with large-scale evaluations? Answer: 1. speed up the rate of genetic change
- can select the best from a large pool
- increase the accuracy of genetic prediction โ how did we get to large-scale evaluations before BLUP? Answer: central tests โ _____ are lists of genetic predictions, accuracy values, and other useful info about sires in a breed Answer: sire summaries โ sire summary predictions are often expressed as ___ Answer: EPDs โ sire summaries represent the expected performance of that sires progeny in a particular trait, relative to the ____ Answer: progeny of other sires โ EPDs are for ____ animals Answer: comparing โ T/F: EPDs do not predict performance per se Answer: true
โ the performance associated with an EPD of ___ should be equivalent to the average performance in a population Answer: zero โ populations can contain genetically diverse ___ and change over time due to selection Answer: contemporary groups โ EPDs should not be compared across ___ Answer: breeds โ ____ is the measure of the strength of the relationship between true values and their predictions Answer: accuracy โ "classical" accuracy would be the correlation between ____ and ____ Answer: true progeny differences and EPDs โ _____: the risk that the true BV or PD will be significantly poorer than expected Answer: selection risk โ the ___ the accuracy of an EPD, the lower the risk Answer: higher โ the accuracy of an EPD tells us nothing about the ____ in offspring performance Answer: variation
โ If you use sire summaries as guides to purchasing, what 2 things do you need to do? Answer: 1. need to know what your particular needs are
- need to read the fine print โ ____ provide much more info than does any visual inspection Answer: EPDs โ EPDs are based on what 3 things? Answer: 1. animals data
- data from relatives
- data from progeny โ EBVs are coming to which species? Answer: dog breeding โ _____: genetic change in one or more traits resulting from selection for another Answer: correlated response to selection โ causes to correlated response to selection: Answer: 1. linkage
- pleiotropy โ _____: one gene affects multiple traits Answer: pleiotropy โ examples of pleiotropy: Answer: spotting, HYPP, G6PD
โ ____ correlation: r BVx, BVy Answer: genetic โ ______ measures the relative importance of pleiotropic effects on 2 traits Answer: genetic correlation โ example of genetic correlation: Answer: milk yield and % milkfat โ _____ correlation: r Px, Py Answer: phenotypic โ example of phenotypic correlation and genetic correlation Answer: birth weight and yearling weight โ _____ correlation: r Ex, Ey Answer: environmental โ ______ is why there is a disparity between genetic and phenotypic correlations (between birth and yearling weight) Answer: environmental correlation โ phenotypic correlation is a function of both ______ and ____ Answer: genotypic and environmental correlations
โ change in BV of trait y, given trait x = Answer: (r)(accuracy)(selection intensity)(variation in BV) / generation interval โ if calculating correlated response to phenotypic selection, the equation would be... Answer: (r)(hx)(hy)(i)(variation in Py) / L โ T/F: in the phenotypic selection correlation equation, heritability is in the formula Answer: False, the square root of heritability is in the formula โ T/F: if you know the response to selection for one trait, you can calculate the correlated rate of response in the other trait Answer: true โ why select for correlated traits? Answer: direct selection may be expensive, inaccurate, or not feasible โ direct selection suffers in ___ if the trait is a ___ Answer: intensity, threshold trait โ correlated trait becomes the ____ trait Answer: indicator; (example: low birth weight for dystopia)
โ if the response to correlated selection/direct selection is <1, ____ selection is better Answer: direct โ use multiple trait selection to.... Answer: improve the aggregate (or net) BV โ ______: select for one trait until you reach your desired selection target, then select for the other trait Answer: tandem selection โ _______: minimum standards for traits undergoing multiple-trait selection Answer: independent culling levels โ independent culling levels are ____ b/c you can't account for temporary environmental effects that animal may overcome with time Answer: risky โ independent culling levels are ____ b/c you don't have to manage culls as breeders Answer: cost-effective โ ______: measures overall economic merit Answer: economic selection index โ index will allow you to keep an animal superior in one trait if it.... Answer: economically overrides another trait
