Animal Breeding and Genetics
Animal Breeding and Genetics APSC 1454
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This 4 page Class Notes was uploaded by Meagan Samele on Wednesday September 7, 2016. The Class Notes belongs to APSC 1454 at Virginia Polytechnic Institute and State University taught by Dr. Wood in Fall 2016. Since its upload, it has received 3 views.
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Date Created: 09/07/16
Animal Breeding and Genetics Chapter 8 ● Genetics works ○ Studies show that genetics can be charted to help solve issues ■ Ex: Amount of milk a cow produces ● Animal Breeding Assumptions ○ Inheritance ■ The algebra of the half ■ Resemblance among relatives ○ Principle of Segregation ■ One allele per gamete ○ Principle of Independent Assortment ■ Separation of one pair of alleles is independent of all other pairs ● The Algebra of the half, and resemblance among relatives ○ Fertilization results in a zygote that contains a full complement of DNA ○ Gametogenesis ■ Meiosis results in ½ the DNA ● Definitions: ○ Allelea particular form of a gene ○ Locus The physical location of a gene ○ Chromosome DNA that contains loci ○ Genotype: All the genes possessed by an animal ○ Phenotype Expression of the gene (physical) ● Sex Chromosomes: ○ Autosomes: nonsex chromosomes ○ Mammals ■ XXhomogametic (female) ■ XYheterogametic (male) ○ Birds ■ ZZMale ■ ZWFemale ○ Traits ■ Sexlimited (autosomal)limited because of hormone development ● Ex: Lactationonly females ■ Sexlinked (sex chromosome) ● Feathering Rate ■ Sexinfluenced (autosomal) ● Horn size (males are bigger) ● Gene ExpressionOne Locus ○ Dominance: denoted with capital letters ○ Recessive:Use lower case letters ○ Codominant (lack of dominance): both alleles expressed in phenotype ○ Incomplete Dominance: heterozygote is intermediate ○ Overdominance: Heterozygote is preferred to either homozygote ○ NOTE: May involve multiple (n>alleles) ● Gene Combinations ○ 6 possible mating types per pair of alleles ■ AAxAA ■ AAxAa ■ AAxaa ■ AaxAa ■ Aaxaa ■ Aaxaa Possible results of AaxAa A a A AA Aa a Aa aa AaxAa ¼ AA ½ Aa ¼ aa ● Allelic Gene Actions (Interactions) ○ Crate of gain=0.1 lbs/day ○ c rate of gain= 0.05 lbs/day ■ Lack of Dominance=Additive Gene Action (add together)’ ● Overdominance=Heterosis ○ Heterozygous is better than average of either parents ○ Useful heterosis ● Epistatic Gene Actions ○ Epistasis=interaction of nonallelic genes ○ Locus #1coat color gene locus:Black (B)/Chocolate (b) ○ Locus #2: expression gene locus : E=yes, e=no ○ Labrador Retrievers: Locus #1 Locus #2 Phenotype B_ E_ Black bb E_ Chocolate __ ee Yellow ● Qualitative Traits Controlled by one or a few genes ○ Coat color in Angus Cattlecomplete dominance ○ Gene: ■ Bblack ■ bred Genotypes Phenotyoes BB Black Bb Black bb Red ● Polledness in Cattlecomplete dominance ○ Ppolled ○ phorned Genotypes Phenotype PP Polled Pp Polled pp Horned ● Mating of heterozygous black. Heterozygous polled parents ○ Possible gametes: BP, Bp, bP, bp Genotypes Phenotypes 1 BBPP, 2BBPp, 2BbPP, 4 BbPp 9 Black & polled 1 BBpp, 2Bbpp 3 Black and Horned 1 bbPP, 2 bbPp ● Mating BbPP x BBPp (practice) Genotypes Phenotypes
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