Fish Genetics PDF

FISH Genetics Tereso A. Abella Professor Emeritus College of Fisheries  GENETICS The study of heredity The study of how differences between individuals are transmitted from one generation to the next The study of how information in the genes is used in...

FISH Genetics Tereso A. Abella Professor Emeritus College of Fisheries  GENETICS The study of heredity The study of how differences between individuals are transmitted from one generation to the next The study of how information in the genes is used in the development and functioning of the adult organism Autosomal Phenotypes Sex Chromosome Chromosomes that usually determine individual”s sex - Morphlogically different in male amd female XY – Male O. niloticus XX - Female ZZ - Male O. aureus WZ - Female ` P = G + E + GxE P = Phenotype G = Genotype E = Environment G x E = Genotype and Environmental Interaction QUALITATIVE PHENOTYPES  Complete Dominant Gene Action Occurs when one allele is expressed more strongly, than the other Example: Coloration in Channel catfish (Normal vs Albino) AA x aa = Aa Aa x Aa  Incomplete Dominant Gene Action Occurs when the dominant allele expresses itself more strongly than the recessive allele, but not strongly enough to make the heterozygous phenotype identical to the heterozygous dominant phenotype. Example: Siamese fighting fish (Steel blue, blue, green)  Additive Gene Action When neither allele is dominant, both contribute equally to the production of the phenotype in a unidirectional additive stepwise manner, and the heterozygotes phenotype is intermediate between the two homozygous phenotypes Example: Rainbow Trout (Golden, palomino, normally pigmented) QUANTITATIVE GENETICS Quantitative Phenotypes - characteristics that are measured - continuous characteristics - production traits (weight, length, dressing %, grams, fat content and fecundity Nature of Quantitative Phenotypes Each phenotype comprises only one distinct category Variations within quantitative phenotypes are not given descriptive identities In a population, quantitative phenotypes are described by their central tendencies and the distributions around those tendencies: mean, variance, standard deviation, coefficient of variation and range Controlled by polygenic genes 300 Chickens 200 Dairy cows Pigs Norwegian salmon 100 Wild fish 1940 1950 1960 1970 1980 1990 2000 Year Development of productivity in farm animals and finfishes (Source: Gjedrem, T. (1993)  Quantitative Phenotypic Variation and its Components : Why do they exhibit continuous variation? Though each gene follows a Mendelian genetics and that the two alleles at each locus segregate during meiosis so that a gamete will receive only one of these alleles; All phenotypes are controlled to some extent by the environment (a phenotype cannot be expressed unless the chemical precursors – proteins, carbohydrates, fats, vitamins, minerals – are provided in the diet Quantitative Phenotypic Variation 𝑉𝑃 = 𝑉𝐺 + 𝑉𝐸 + 𝑉𝐺−𝐸 𝑉𝑃 = Phenotypic Variance 𝑉𝐺 = Genotypic Variance 𝑉𝐸 = Environmental Variance 𝑉𝐺−𝐸 = Interaction of genetic and environmental variances Genetic Variance - component of greatest importance - change the genetics of a population to improve productivity 𝑉𝐺 = 𝑉𝐴 + 𝑉𝐷 + 𝑉𝐼 𝑉𝐺 = Genetic Variance 𝑉𝐴 = Additive Variance 𝑉𝐷 = Dominance Genetic Variance 𝑉𝐼 = Epistatic Genetic Variance Dominant Genetic Variance Variance that is due to the interaction of alleles at each locus Epistatic Genetic Variance Variance that is due to the interaction of alleles between two or more loci Additive Genetic Variance The component that is due to the additive effect of the genes. It is the sum of the effect of all alleles across all loci  𝑉𝐴 vs 𝑉𝐷 𝑉𝐴, is exploited by selection, 𝑉𝐷 is exploited by hybridization Additive Genetic Variance and Selection Selection is a breeding program in which individuals or families are chosen in an effort to change the population mean in the next generation. - selection is based on minimal performance levels. Fish that exceed minimal performance levels will be selected (SAVED) and use as broodstock; those that fall below minimal performance levels will be culled (REMOVED) Types of Selection Program Mass Selection – Choosing the best individuals in the population. This is the most common method, by far. It is also the easiest to understand and perform. (-) asynchronous breeding confounds variance of age and growth rate, and introduces time-dependent variance if the environment is seasonal (-) trade-off between selection intensity and inbreeding (-) variance caused by competition is maximized Mass Selection (-) unrecorded variation in fecundity causes inbreeding ( ) workload and use of facilities fluctuates widely and the capacity of the whole system is limited by the number of animals which can be spawned siumultaneously Between Family Selection Choosing all the individuals from the best families (+) Competition effects between families are eliminated (-) Uses a lot of space per family, thus maximizing the problem of trade-off between selection intensity, inbreeding and common environment variance ( ) Workload and use of facilities fluctuates widely Within Family Selection Choosing the best individuals in each family (+) Eliminates the age-growth confusion in 𝑉𝑃 (+) Eliminates common-environment variance component, including the competitive effects (++) no trade-off between selection intensity, inbreeding and variances ( ) Evens out and t the workload and makes full use of the facilities throughout the cycle  FAMILIES FISH NO. A B C D E 1 90 g 115 g 105 g 80 g 95 g 2 85 110 93 100 98 3 108 80 120 98 100 4 96 94 87 107 98 5 100 90 84 92 100 6 117 98 100 99 112 7 88 116 93 104 110 8 114 113 89 114 89 9 105 93 84 118 103 10 87 108 98 96 104 Mean, X 99 g 101.7 g 95.3 g 100.8 g 100.9 g Heritability (h2) - The proportionate amount of additive genetic variance - h2 = V / V A P 2 R=h S R = response to selection 2 h = heritability S = selection differential Hybridization -Mating of two different breeds, strains, or species Uses of Hybridization a) Use as a “quick and dirty” method before selection will be employed b) When heritability is small, hybridization is often the only practical way to improve productivity c) Production of new breeds or strains d) Production of uniform products e) Production of monosex populations f) Production of hybrids for “sea ranching” Biotechnology in Aquaculture Genetic Improvement: Selective Improvement Disease Management Nutrition Environmental Management Reproductive Technologies Molecular Biology Tools Production of High-Value Compounds Bioinformatics Biotechnology in Aquaculture Genetic Improvement: Selective Improvement Selective Breeding Biotechnology in Aquaculture Genetic Improvement: Selective Improvement Selective Breeding Transgenic Fish Biotechnology in Aquaculture Disease Management Vaccines Biotechnology in Aquaculture Disease Management Vaccines Probiotics and Biocontrol Agents Biotechnology in Aquaculture Nutrition GMO Feed Ingredients Biotechnology in Aquaculture Nutrition GMO Feed Ingredients Enzymes and Additives Biotechnology in Aquaculture Environmental Management Bioremediation Biotechnology in Aquaculture Environmental Management Bioremediation Biofloc Technology Biotechnology in Aquaculture Reproductive Technologies Induced Breeding Biotechnology in Aquaculture Reproductive Technologies Induced Breeding Cryopreservation Biotechnology in Aquaculture Molecular Biology Tools DNA Barcoding and Genomics Biotechnology in Aquaculture Molecular Biology Tools DNA Barcoding and Genomics Marker-Assisted Selection Biotechnology in Aquaculture Production of High-Value Compounds Bioactive Molecules Biotechnology in Aquaculture Bioinformatics Data Analysis and Management Biotechnology Cellular aquaculture GOOD LUCK ON YOUR BOARD EXAM