ANS 2: Week 9 Notes
ANS 2: Week 9 Notes ANS 002
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This 7 page Class Notes was uploaded by Mackenzie Hayes on Friday May 27, 2016. The Class Notes belongs to ANS 002 at University of California - Davis taught by Dr. James Murray in Spring 2016. Since its upload, it has received 15 views. For similar materials see Introductory Animal Science in Animal Science at University of California - Davis.
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Date Created: 05/27/16
ANS 2: Week 9 Notes (5/23) ● Gene Frequencies ○ Individualscan only have 2 alleles at each locus ○ Population can have many alleles at each locus ■ Look at allele frequencies for population ● Hardy-Weinberg Equilibrium: ○ Determines predictions for following generations’ allele frequencies ○ For specific populations ○ p/q = each get assigned to an allele ■ P + q = 1 ■ Given one allele’s frequency can determine the other ■ Use to determine population’s frequencies ● P 2+ 2pq + q= 1 ○ Can identify “bad” genes and remove them from the population ■ Cystic Fibrosis ■ If bad gene accompanies a good gene close together on a chromosome, they will travel together during meiosis ● Makes it hard to separate and select against ● Other Terminology: ○ Heritability: ■ Always between 0 and 1 ■ if it’s very low, it is hard to improve upon by selection ■ If it is high, it is easy to select for ● Variance: ○ The amount of variation is measured and expressed as variance ○ Phenotypic variance : ■ Result of the effects of genetic predisposition and environmental effects ■ Job of statistics is to separate genetic from environmental causes ○ Once genetic variance is known ■ Can be used to identify superior animals ○ Genotypic Variance : ■ Variance between individuals in their genetically determined potential ■ Genetic factors that can be transmitted to the next generation (additive variance) ■ Genetic factors that are unique to the animal ○ Additive Genetic Variance: ■ Component that can be transmitted to the next generation ■ Breeding value: genetic value of an individual for a specific trait ● Population specific ● Ie: difference between the mean value of its progeny compared with the mean value of the population in which it is bred ● Thus breeding value is specific to the population in which it has offspring ○ Non-additive genetic Variance: ■ All genetic variability that is unique to individual ■ Arises from dominance, epistatic, and epigenetic effects that are unique to the genotype of the individual ● Heritability: ○ Proportion of observed variability of a trait that is genetic in nature ■ Can have some impact through passing on to next generation ○ Breeder can’t do anything if it’s all due to environments ○ Variance in Additive Genetics / Variance of the Phenotype ○ Degree of relationship between genotype and phenotype ■ If “leanness” has a high heritability → more lean offspring due to more lean alleles being passed on ● *Assume Variation is a Bell Shaped Curve* ● Selection Differential: ○ The difference between selected animals and average of all animals in the herd (5/25) ● Mendel ○ Focused on a few very specific traits with a couple of alleles ○ On different chromosomes (not linked) ○ Knew nothing about chromosomes and genetics ■ Only knew 3:1 phenotypic ratio of dominant:recessive ○ Principles of Segregation ■ More than one determinant ■ They would segregate going through reproduction process ○ Principle of Independent Assortment ■ Separated independently of each other ■ Just so happened to be because they’re on different chromosomes ● The further away alleles are, the more likely they will segregate independently ● Exception to Mendel’s rules: ○ Linked genes - don’t sort independently ■ More likely to segregate together ■ Less likely to cross over each other (very rare) ○ Genes on sex chromosomes ○ Mitochondrial genes ○ Meiotic-drive mechanisms ■ Allele going to show up in the gametes more frequently than it should according to chromosomes ● Should show up half and half but ISN’T true for this ● Meiotic drive = advantage of a certain allele of another ○ If one allele is detrimental (kills gametes) ○ The other allele will be better passed on ○ Imprinted genes (epigenetics) ■ Depends upon the parental origin of the allele ● (may express one parental trait from father but not from mother) ● Inbreeding: ○ Mating of individuals related by descent ○ IBD = identical by descent ■ Alleles that are identical copies of an allele present in a common ancestor ■ Ex. blood type ○ Inbreeding depression ■ Reduction in fitness (survival, reproduction) ○ The higher the inbreeding coefficient, the more detrimental on survival ■ California condors have such a small population that it’s very inbred ● They’re all captured every year and carefully cared for ● Consequences of inbreeding: ○ Loss of genetic diversity increase risk of extinction ■ Cheetahs - least diversity of any mammal ○ Reduces reproductive fitness in naturally out-breeding species ○ Increases risk of extinction in captive and wild populations ○ Loss of genetic diversity reduces ability of species to evolve with change ● Genetic Drift: ○ 1. A result of binomial sampling in small populations ○ 2. More effective in small populations than large populations ○ 3. Alleles could be either fixed or lost by chance ○ In small populations you can by chance get more or less frequency of a specific allele than you probably should ■ Like flipping a coin 10 times and getting all heads vs 1000 times ■ That’s why hardy-weinberg is based on large population size ● Biotechnology in Animal Agriculture ○ Pigs, Cattle, Goats, Sheep, Rabbits, Fish, Chickens ● What is biotechnology? ○ Artificial insemination ○ Embryo transfer ○ rDNA produced diagnostics, vaccines, biologics ○ Marker assisted selection - whole genome selection ○ Cloning ○ Genetic engineering + gene editing ● Uses: ○ Cryopreservation of sperm, ova, gonads, and embryos ○ Manipulation of embryos: transfer, cloning, ICSI, genetic engineering, gene editing ○ Stem cells ● Diagnostics: Genetics disease (VGL) veterinary genetics lab ○ Horses, dogs, cats, elk, sheep (5/27) ● PCR with bacteria to test what is in the bacteria around the world ○ Anthrax- deadly, put into envelopes to Congressmen- used to find strain ○ Listeria in raw milk is lethal ○ Fungi and bacteria are identified strains of pathogens ● PCR = polymerase chain reaction ○ a method of amplifying small amounts of DNA ○ need to know sequence to make specific primers ● Animal Biotechnology- Viruses ○ Recombinant DNA and RNA vaccines ○ Plasmid and viral vector delivery ○ Vaccina and adeno-associated virus ● Multiple vaccines in one system ○ Lire virus vaccine- kill a little, not too much ○ Dead virus vaccine- still works ○ Break bacteria into bacterial wall ○ Bacterial plasmid ○ Use vaccina to vaccinate against diseases ○ Make multi multi-valent vaccine and insert different antigens into one vaccine ○ Insert DNA that makes antigen ● rVaccines ○ rabies, parvovirus, kennel cough, lyme disease, salmonella ■ Removed rabies from Belgium by picking out rabies areas with animals ● Vaccines ○ Rabies ○ Recombinant vaccine V-RG ○ Inserted rabies glycoprotein gene (the antigen) into vaccina virus (cow pox) ○ Harmless to humans ○ Succesfully used in the field ○ Stable under relatively high temperatures ○ Can be delivered orally ● Marker Assisted Selection ● Against diseases ○ cattle: BLAD, Weaver syndrome ○ horses: HYPP, SCID, LWFS, CA ○ pigs: halothane sensitivity ● For production traits ○ cattle: milk production, meat quality ○ pigs: litter size, meat quality ○ horses: coat color ○ goats: α-S1-casein ● Marker or whole genome selection ● Selection for markets for better quality meat- even if don’t have genes, thousands of at a time based on markers ● Cloning ○ the asexual reproduction of a genetically (nuclear) identical individual ● History ○ 1981 - Embryo splitting ○ 1987 - Blastomere fusion to an enucleated oocyte ○ 1997 – Adult somatic cell nuclear transfer ● Take out polar body and add a nucleus into empty egg- 3n would die, could grow into whole animal now ○ Pronucleated cell ○ Use electrodes to fuse membranes of cell to the ovocyte, the egg thinks it has been fertilized and begins development ○ Sheep are the hardest to clone ○ Cows and pigs are easier to clone ○ Goats cloned in troptes are harder to clone compared to temperate ○ Not efficient> not production, but resurrect elite dead bulls to good cows.
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