ASC 362 Final Study Guide fully solved & updated

Accuracy - ANSWER-a measure of strength of the relationship between true values and their predictions for a trait; a value that describes reliability of an estimate Animal Model - ANSWER-An advanced statistical model for genetic prediction that is used to evaluate all animals in a population; BLUP is an example Best Linear Unbiased Prediction (BLUP) - ANSWER-A method of genetic prediction that is particularly appropriate when data come from genetically diverse contemporary groups Breed Complementarity - ANSWER-an improvement in the overall performance of crossbred offspring resulting from crossing breeds of different but complementary biological types; when the characteristics of different breeds complement each other in crossbreeding systems Breeding Value - ANSWER-breeding effects that are consistently transmitted from parents to progeny; the additive genetic worth of an animal relative to some base population; the worth of an individual as a (genetic) parent Collateral Relatives - ANSWER-relatives that are neither direct ancestors nor direct descendants of an individual, e.g.: siblings, aunts, uncles, nieces, and nephews. Contemporary Group - ANSWER-a group of animals that have experienced a similar environment with respect to expression of a trait. usually same location, breed, sex, similar age and management. Used to account for contemporary group effects, e.g. environmental effects that are common to all members of the group Crossbreeding - ANSWER-the mating of sires of one breed or breed combination to dams of another breed or breed combination Direct Effect - ANSWER-the effect of an individual's genes on its performance Direct Selection - ANSWER-selection for a trait as a means of improving that same trait Estimated Breeding Value (EBV) - ANSWER-prediction of genetic value derived from the application of genetic theory and statistics to performance records; estimate of unknown breeding value. Stated in general terms, the EBV equals twice the EPD when both are expressed as deviations from the average. Expected Progeny Difference (EPD) - ANSWER-an estimate, or prediction, of how much better or poorer and individual's progeny will perform compared to the average of all individuals in the breed; an EPD is one half the EBV for an animal Full Sibs - ANSWER-animals that have the same sire and dam Generation Interval - ANSWER-In a herd or flock, the average age of parents with offspring are born; the amount of time required to replace one generation within the next. Genetic Correlation - ANSWER-a measure of the strength of the relationship between breeding values for one trait and breeding values for another trait. the situation in which the same or many of the same genes control two traits; a measure of pleiotropy. Half Sibs - ANSWER-animals that have either the same sire or the same dam. Half-brothers and half-sisters Heritability (Broad Sense, Narrow Sense) - ANSWER-a measure of strength between breeding values and phenotypic values for a trait in a population. Narrow Sense: additive gene effects Broad Sense: total variation due to genetics Heterosis (Individual, Maternal, Paternal) - ANSWER-the superiority of a crossbred individual relative to the average performance of the purebred parents included in the cross Hybrid Vigor - ANSWER-an increase in the performance of hybrids over that of purebreds, most noticeably in traits like fertility and survivability Indirect Selection - ANSWER-selection for one trait as a means of improving a genetically correlated trait Large-Scale Genetic Evaluation - ANSWER-the genetic evaluation of large populations--typically entire breeds Maternal Effects - ANSWER-any environmental influence that the dam contributes to the phenotype of her offspring (mothering ability, milk production, maternal instinct). The genetics of the dam allow her to create this environment for her offspring. Maternal effects are important during the nursing period but have diminishing effects post weaning. Outbreeding (outcrossing) - ANSWER-the mating of animals less closely related that the overage relationship within the breed or population concerned; opposite effect of inbreeding; Outcrossing and crossbreeding are examples. Pleiotropy - ANSWER-the phenomenon of a single gene affecting more than one trait Prepotency - ANSWER-the ability of an individual to produce progeny whose performance is especially like its own and/or is especially uniform. One consequence of the increase in homozygosity caused by inbreeding is greater prepotency in inbreds. Response to selection (genetic change) - ANSWER-the rate of change in the mean breeding value of a population caused by selection Rotational Cross - ANSWER-generations of females are rotated among sire breeds in such a way that they are mated to sires whose breed composition is most different from their own; a crossbreeding system designed to maintain high levels of heterosis while also allowing conventional female production within a herd or flock. Based on alternating use of males of 2, 3, or more breeds within the herd or flock. Selection - ANSWER-the practice of determining which individuals will be allowed to mate to produce the next generation; it is the process breeders use to produce genetic change Selection Differential - ANSWER-refers to how much better or worse the selected individuals are compared to the entire group of individuals eligible for selection; measured as the difference in the mean of those chosen to be parents and the mean of the group for a particular trait Selection Intensity - ANSWER-A measure of how "choosy" breeders are in deciding which individuals are selected. the smaller the proportion of offspring that needs to be saved for replacements, the greater the selection intensity and, therefore, the larger the selection differential. Terminal Cross - ANSWER-a system designed to make maximum use of both heterosis and complementarity by crossing two, three, or four breeds. what happens to selection response as heritability increases? - ANSWER-R=h^2 x SD. what happens to selection response as we increase selection intensity? - ANSWER-R=h^2 x i x (sigma)p. what happens to selection response as generation interval increases? - ANSWER-R/yr=(R/generation)/L what four factors affect response to selection? - ANSWER-selection differential, heritability, generation interval, genetic correlation when would you expect the selection differential to be negative? - ANSWER-when the economically desired trait is below average for the group explain selection intensity. can it be either positive or negative? when? - ANSWER-a measure of how "choosy" animal breeders are in deciding which individuals are selected to be parents. yes what would be typical generation intervals for several types of farm animals? (average, sires, dams) Is the generation interval the same for sires and dams? which is usually longer? why? - ANSWER-species, male, female: cattle, 3-4, 4.5-6, sheep, 2-3, 4-4.5, swine, 1.5-2, 1.5-3, horses, 8-12, 8-12, chickens, 1-1.5, 1-15 of what value is knowing whether or not traits are genetically correlated? - ANSWER-helps determine pleiotropy, helps determine whether better to use indirect or direct selection what is the general form of the equation for EBV? - ANSWER-EBV=.5 x (BV sire) + .5 x (BV dam), EBV=b(P-P_) what is the general form of the equation for accuracy? - ANSWER-ACC=,/b x g what is the general form of the equation for EPD? - ANSWER-EPD=.5 x EBV what types of relatives can be used in the estimation of breeding value? - ANSWER-full sibs, half sibs, progeny, parents, grandparents what is used to express the degree of confidence in an estimate of breeding value? - ANSWER-accuracy why is pedigree information not a very useful source of information for estimating breeding value? - ANSWER-limited number of ancestors, and the utility of each ancestor's record diminishes rapidly if it is from 3+ generations back what are two reasons for sibs to be similar? - ANSWER-some fraction of their genes in the common because they share a common ancestry, frequently reared in similar circumstances is inclusion of information on relatives important for traits with low heritability or traits with high heritability? explain. - ANSWER-high heritability. As heritability increases, so does accuracy An angus bull has a YW EPD of +20. Is this higher than average? explain. - ANSWER-yes, it is a (+) deviation from the mean what is the primary effect of inbreeding? secondary effects? - ANSWER-increase in homozygosity, inbreeding depression which types of traits are affected most by inbreeding? which are lease affected? - ANSWER-reproductive traits=high, growth traits=moderate, carcass traits=low explain the concept of inbreeding depression. - ANSWER-decline in performance due to inbreeding what determines the common ancestor in a pedigree? - ANSWER-an individual that appears on both the sire and the dam sides of the pedigree. what are the steps involved in calculating an inbreeding coefficient? a relationship coefficient? - ANSWER-Inbreeding coefficient: generate arrow pedigree, list all paths that connect the sire and the dam, locate the common ancestor in each path, determine inbreeding coefficient for each common ancestor, count number of arrows in each path to determine 'n' (will use n+1), calculate the value of each path connecting sire and dam, add together the value for each path. Relationship coefficient: generate arrow pedigree, list all paths that connect progeny and common ancestor, calculate inbreeding coefficient of common ancestor, count number of arrows in each path to determine 'n', calculate value of each path, add together values for each path, divide by value in denominator what is the primary effect of crossbreeding? secondary effects? - ANSWER-heterosis, breed complementarity explain the concept of heterosis. What traits exhibit low levels of heterosis? moderate levels? high levels? how does this compare to traits that are affected least by inbreeding depression? most affected by inbreeding depression? how does this compare to traits that are highly, moderately, and lowly heritable? - ANSWER-High heterosis=reproductive traits, moderate heterosis=growth traits, low heterosis=growth traits. This is the same as inbreeding depression traits. Exactly the reverse of general levels of heritability for these classes of traits. how is breed complementarity a benefit of crossbreeding? - ANSWER-the advantage gained from using an optimum combination of breeds compare terminal versus rotational crossbreeding systems (**review) - ANSWER-terminal: specific breed of sire related to specific breed of ram rotational: generate their own replacement females