An Sci 361 1st Edition Lecture 11 Outline of Last Lecture I. Populationa. Calculationsi. Counting Methodii. FormulaII. Hardy-Weinberg Equilibriuma. Calculationsb. 4 forces that change gene frequencyOutline of Current Lecture I. Simply-Inherited Traitsa. Breeding Approachesb. ExamplesII. Polygenic Traitsa. Breeding Approachesb. ExamplesIII. LociIV. Threshold TraitsCurrent Lecture- Simply-Inherited Traitso All simply-inherited traits are influenced by a few alleles at one or a few loci o Most simply-inherited traits are: Defined by discrete categories (qualitative) Not affected by the environment- Phenotype = Genotype Examples:- Polled or horned in cattle and sheep- Black or red coat color in cattle and pigs- Rose comb or single comb in chickens- Long ears, medium length ears, or no ears in goats- Black, chocolate, or yellow in Labrador dogs- Polygenic Traitso All polygenic traits are influenced by a few to several alleles at many loci, and most of the alleles have a small effect on the trait o Most polygenic traits:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Are continuous in their measurement (quantitative) – the trait can have an infinite number of values Tend to be normally distributed within a large population – they follow a bell-shaped curve Are affected by the environment- Phenotype = Genotype + Environment (Environment usually has greater effect on phenotype than genotype) Examples:- Milk production in dairy cattle, goat, and sheep- Average daily gain in growing beef cattle, pigs, and sheep- Speed in race horses and dogs- Egg production in poultry- Body weight in all animals- From Single Loci to Quantitative Traitso One locus, two alleles: Freq. A = p = 0.5; Freq. a = q = 0.5- A = 1 ounce of increased wool production- a = 0 ounces of increased wool production- Freq. AA = p2 = P = 0.25- Freq. Aa = 2pq = H = 0.50- Freq. aa = q2 = Q = 0.25 Co-dominance: - AA = 2, Aa = 1, aa = 0 ounces of increased woolo Two loci, each with 2 alleles Freq. A = p1 = 0.5; Freq. a = q1 = 0.5 Freq. B = p2 = 0.5; Freq. b = q2 = 0.5- A & B = 1 ounce of increased wool production- a & b = 0 ounces of increased wool productiono As the number of loci influencing the trait increases, the distribution of genotypes and phenotypes becomes continuous and often tends to fit a normal distribution.- Threshold Traitso A special type of polygenic trait Influenced by a few to several alleles at several loci Most of the alleles have a small effect on the trait Affected by the environment- Phenotype = Genotype + Environment Defined by discrete categorieso Examples: Dystocia (difficult birth):- No, some, moderate, or great assistance necessary Disorders (e.g. hip dysplasia in dogs): - Affected or not affected Conception rate: fertility or no fertilitySimply-Inherited PolygenicQualitative Coat color,Polled/HornedCalving Ease,Conception,Litter SizeQuantitative Fat Thickness,Milk Yield*Calving ease = Threshold traito Examples: Dwarfism (body size) Double muscling (muscle mass) - Mutations on Myostatin gene- Breeding Approaches for Simply-Inherited and Polygenic Traitso Notice: Both simply-inherited and polygenic traits are subject to the same Mendelian ruleso F However: With simply-inherited traits: identification of effects of individual genes and gene combinations; test mating to uncover unknown genotypes  With polygenic traits: statistical models to predict genetic value of animals (estimated breeding value, expected progeny difference, transmitting ability,