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67 Cards in this Set
- Front
- Back
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What are qualitative traits?
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Those for which phenotypes can be classified into groups rather than numerically measured (single gene)
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What are quantitative traits?
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Those that are numerically measured and are usually controlled by many genes, having a small effect (economically important)
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What are sex-linked traits?
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Traits genetically controlled by genes located on the sex chromosomes
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What are examples of sex-linked traits?
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Hemophelia, colorblindess (controlled by a gene on x chromosome)
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What are sex limited traits?
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Traits that are expressed in only one sex
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What are examples of sex limited traits?
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Milk production, egg production, cryptochidism
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What is cryptochidism?
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Male in which testes don't complete the migration into the scrotum (either unilateral or bilateral)
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What is selection?
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Determining which animals will reproduce
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What is natural selection?
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Mating of animals in a natural environment
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What is artificial selection?
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Humans dictate breeding of animals (ex. castration)
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What is inbreeding?
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Production of progeny by parents more closely related than the average of the population fro which they came, mating of relatives (more closely related, the higher the degree of inbreeding)
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What is the purpose of inbreeding?
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Consistency, eliminates problem genes
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Why do most livestock producers avoid inbreeding?
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Because they associate it with the appearance of genetic defects and an overall decline in vigor and performance (the oversimplification is simply not justified)
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What is inbreeding depression?
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A loss of reduction of vigor, viability, or production that usually accompanies inbreeding
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Does inbreeding cause bad genes?
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No, it just causes them to be expressed
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What is the genetic effect of inbreeding?
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The creation of more pairs of homozygous genes. Thus animals are more likely to "breed true"
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True or false: Inbreeding does not increase the number of recessive genes in the population, it merely allows them to be expressed
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True
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What is intensive inbreeding?
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Mating closely related animals for many generations
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What is line breeding?
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Mild form where inbreeding is kept low. Keep high genetic relationship (2nd or 3rd cousins)
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What is the opposite of inbreeding?
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Cross/Hybrid Breeding
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What are superior genetics?
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High homozygous and likely to pass on
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What are the phenotype effects of inbreeding?
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Depression of traits related to physical fitness (fertility, viability, and growth rate) Animals are less vigorous
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What is high inbreeding usually detrimental to?
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It is usually detrimental to reproductive performance, preweaning, and postweaning growth
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What does high inbreeding make animals for susceptible to?
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Environmental stress
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What happens to 60-70% of inbreeds?
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Detrimental effects
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What happens to 30-40% of inbreeds?
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Show no effect and posses improved productivity
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What is heterosis?
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Crossing of inbred lines
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How do we use inbreeding in livestock production?
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1. crossing of inbred lines
2.quickly identifies some desirable and undesirable genes 3. Inbred animals with superior performance generally have superior breeding values and uniform progeny 4. Crossing inbred lines- heterosis compensates for inbreeding depression |
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What quickly identifies some desirable and undesirable genes?
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Inbreeding (livestock production)
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What is outcrossing?
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Unrelated animals within the same breed are mated, gene pairs are primarily heterozygous, most popular system
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What is the most popular system?
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Outcrossing
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In outcrossing, the gene pairs are primarily what?
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Heterozygous
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What type of breeding is the most commercial?
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Crossbreeding
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What is hybrid vigor?
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"the superiority of the crossbred offspring over the average of the pure breeds (parents) used to make the cross"
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What are the two primary reasons to crossbreed?
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Heterosis and complimentary of traits
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What is strain crossing?
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Cross two strains of similar egg production
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What are cross inbred lines?
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Brother to sister mating up to five generations, used in 4 way crosses hybrid chickens
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What is the preferred system of mating for commercial swine production?
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Crossbreeding
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What is rotational?
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Combines two or more breeds, where a different breed of boar is mated to a replacement crossbred female produced by the previous generation
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What is terminal?
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Don't keep offspring for replacement females, none kept for breeding
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What is simple cross?
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A two breed single or rotational female is bred is mated to boar of a third breed
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What is complex cross?
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Uses four breeds, crossbred boards are mated to crossbred females
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What is the main mating system in horses?
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Line breeding
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What is tandem?
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Looking at one trait at a time until desired level is obtained (slow, inefficient)
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What are independent culling levels?
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Set minimum levels for each trait and cull animals that don't fit (good method)
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What is selection index?
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Each animal is rated numerically in comparison to others (best to worst) and then the numbers added to determine the best animal
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What is the definition of growth?
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increase in body weight until maturity is reached (muscle, fat, bone)
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What is the definition of true growth?
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The growth that involves an increase in structural tissues (excludes fat as storage tissue)
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True or false: a human can still be growing, just not experiencing true growth
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True
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What is development?
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Directive coordination of all diverse processes until maturity is reached, involves growth, cellular differentiation, and changes in body shape
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What is development controlled by?
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Genetic make up of the animal
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What is the definition of maturity?
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The state of being fully grown or developed
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What two types of maturity are there?
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Sexual and compositional
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What is sexual maturity?
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Ability to breed
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What is compositional maturity?
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Feedlot animals with yield grade 2 choice
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What is chronological age?
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The age in terms of units of time (10 months old)
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What is physiological age?
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Stages of development as the animal grows from conception to maturity (heifer is cycling, puberty)
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What is hyperplasia?
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Increase in the number of cells
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What is hypertrophy?
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Increase in cell size
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True or false: You are either born with muscle or not
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True
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What is efficiency in production defined as?
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Units of input per unit of output
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Is growth linear?
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No
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When does true growth stop?
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When animal reaches maturity
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What is true growth defined as?
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Increase in body protein
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What are the types of tissue?
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nervous, skeletal, muscle, fat
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What are the types of body area?
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head, neck&shoulder, hind limb, rib&loin
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What are the types of fat deposit?
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perinephric, intermuscular, subcutaneous, intramuscular
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