(PPT) FISH GENETICS MANIPULATION BY: NKUKURAH, D.K

Views:
 
Category: Entertainment
     
 

Presentation Description

GROW YOUR AND OWN FISH

Comments

Presentation Transcript

PowerPoint Presentation:

Fish Genetic Issues in Reproduction NKUKURAH, D.K nkukurahd@yahoo.com

PowerPoint Presentation:

Genetics: What is it? Genetics : The science of heredity and variation. Heredity : transmission from generation to generation (usually through the process of reproduction) factors which cause the offspring to resemble their parents (or not.)

PowerPoint Presentation:

Genetics Terms Selective breeding -the choosing of individuals of a single strain and spp. Hybridization -the crossing of different spp. Crossbreeding -the mating of unrelated strains of the same spp. to avoid inbreeding

PowerPoint Presentation:

Selective Breeding “Artifical selection” as opposed to natural selection, results in reducing genetic variability in a population. Could be considered inbreeding if not closely monitored. If selective breeding involves excessive inbreeding physical abnormalities, metabolic deficiencies, and developmental abnormalities may occur. Inbreeding depression-loss of fitness due to inbreeding more likely to observe occurence of recessive traits Decrease in heterozygosity

PowerPoint Presentation:

Selective Breeding Although potential for deleterious results, selective breeding rationalized by: size color shape better FCR reproductive capacity disease resistance

PowerPoint Presentation:

Already looked at hybrid striped bass. What other examples are out there?? Splake -brook trout/lake trout, Tiger Musky-northern pike/musky Sunfish hybrids (many combinations) Hopefully achieve “hybrid vigor,” at least in some trait. Most true hybrids are sterile, but not all Hybridization

PowerPoint Presentation:

Gynogenesis Development of an ovum without fusion of gametes usually haploid and die sometimes diploid larva develop requires retention of 2 nd polar body during meiosis Amazon mollies, cruzian carp do this Induced by: radition, chemical, electrical currents, sperm from related species

PowerPoint Presentation:

Regulation of Ploidy Monosex, polyploidy, and beyond…

PowerPoint Presentation:

Visual selection 2. Hybridization 3. Sex-reversal 4. Genetic manipulation Male Populations Mono-sex male tilapia populations can be produced by:

PowerPoint Presentation:

How DO you sex a tilapia?? Begin with 25 to 30 g fish (any smaller and you’ll go blind looking for genital openings.) Males and females can be separated by visual inspection of the genital papilla (next slide). The male genital papilla is pointed and contains only the small urogenital pore which is difficult to observe . The female papilla is rounded and contains a small opening to the urinary duct and a larger oviduct. Selection is usually based on the presence or absence of the oviduct.

PowerPoint Presentation:

How DO you sex a tilapia?? Males are stocked for further growth while females can be used as brood stock or discarded. Visual selection of male tilapia is costly because of the extra labor needed to separate males from females.

PowerPoint Presentation:

Male papilla Female papilla with oviduct anus anus Visual Selection of the Genital Papilla

PowerPoint Presentation:

Using Two Species Two species of tilapia can be crossed to yield all-male offspring. Male Hornorum tilapia can be hybridized with the female Nile tilapia and offspring are all-male. However, the hybrid is fertile and can backcross with female Nile and Hornorum tilapia.

PowerPoint Presentation:

Using Two Species Only genetically pure Hornorum and Nile tilapia will result in 100% male offspring. Maintaining pure lines of Nile and Hornorum tilapia over a long period of time is difficult. Additionally, hybrid fry yield per female is low compared with fry yield from pure species spawns.

PowerPoint Presentation:

Male Hornorum tilapia Female Nile tilapia All-male hybrid tilapia ZZ XX XZ Hybridization

PowerPoint Presentation:

Sex determination by hormones A popular way to produce all-male populations is with hormone sex reversal of fry. Tilapia fry (18 day) are fed a diet containing a male steroid (methyl testosterone) for 20 to 28 days. Females develop as “functional males” following hormone treatment. All-male populations are hard to produce!! ~95 to 98% males are commonly produced .

PowerPoint Presentation:

Sex Reversal of Tilapia Fry

PowerPoint Presentation:

1) XX F + XY M XX + XY normal Genetic Manipulation

PowerPoint Presentation:

More genetic manipulation What if female Nile tilapia are homozygous (XX) and male Nile tilapia are heterozygous (XY) for sex. A pairing of genetically normal male and female Nile tilapia will result in 50% male and 50% female offspring. Now if we feed normal fry estrogen for 28 days, we get phenotypic all-female fry.

PowerPoint Presentation:

1) XX F + XY M estrogen XX F + XY ”F” Genetic Manipulation

PowerPoint Presentation:

However, 50% of these “feminized fry” are genetic females (XX) and 50% are genetic males (XY). These females are individually paired with normal males. A genetic female (XX) paired with a genetic male (XY) will have offspring that are 50% male and 50% female. Females from this crossing are discarded.

PowerPoint Presentation:

1) XX F + XY M estrogen XX F + XY ”F” 2) XY ”F” x XY M XX F + 2 XY M + YY M Genetic Manipulation

PowerPoint Presentation:

When a genetically male female (XY) is crossed with a genetic male (XY) the offspring will be 25% female (XX) and 75% males (50% XY and 25 % YY). Again, individual pairings with a genetic female (XX) are required to determine which male is YY. The YY males or “supermales” will sire 100% male offspring (XY) when paired with genetic (XX) females.

PowerPoint Presentation:

1) XX F + XY M estrogen XX F + XY ”F” 2) XY ”F” x XY M XX F + 2 XY M + YY M 3) XX F x YY M 100% XY M ?? Genetic Manipulation

PowerPoint Presentation:

B) INDIRECT FEMINIZATION. FEMALE HOMOGAMETY F 0 Androgen Treatment XX XY XX F 1 NEOMALE XX F 2 100% female 50% male 50% female XX XY XX XY A) DIRECT FEMINIZATION. ANY GENETIC SYSTEM SEXUALLY UNDIFFERENTIATED FISH ALL- FEMALE STOCK Estrogen Treatment XX

Indirect Feminization:

Indirect Feminization

Many species specific questions:

Many species specific questions Genetic mechanism of sex determination ( gynogenesis ) Timing of gonadal differentiation, labile period Efficacy of direct hormonal sex reversal Reproductive ability of sex reversed fish Differentiating neomales

PowerPoint Presentation:

Indirect Feminization to produce all-female Atlantic halibut stocks XX XX Hormonal sex reversal ** Neomale Broodstock : Genotypic female but phenotypic male XX All females XX masculinization

Steroid hormones and sex differentiation:

Steroid hormones and sex differentiation Testosterone 17ß-Estradiol 11ß-Hydroxytestosterone 11-Ketotestosterone P450 Aromatase 11ß-Hydroxylase 11ß-HSD MALE FEMALE The key steroids for gonadal differentiation in teleost fishes are 17ß-estradiol and 11-ketotestosterone. The critical enzymes in the synthesis of these compounds are P450 aromatase and 11ß-hydroxyalase, respectively. Ovarian development Testicular development Bipotential Undifferentiated gonad Species specific labile period Some species temperature (ESD) etc influence gonadal development, or combination

PowerPoint Presentation:

Transgenics: How do you get a transgenic fish? Transgenic or genetically engineered animals are developed by inserting single or multiple genes from one species into the DNA of another species. Three basic steps: Isolate and identify the genes that posses the desired trait. Genes may come from similar fish species, plants, bacteria, animals, and even humans. Insert isolated material into the intended target fish’s eggs. Grow your fish!!

PowerPoint Presentation:

Differences in terms? The terms genetically engineered, genetically modified, and transgenic are used synonymously. The term transgenic arises from the procedure of transgenesis, one method in which scientists have successfully inserted genes from one species to another.

PowerPoint Presentation:

What is a triploid fish? Triploid fish contain three sex chromosomes. Heat and or pressure applied to females’ eggs to generate the extra chromosome. Proponents of G-EN suggest environmental risks associated with their release into open water would be rendered harmless. No guarantee of sterility!! Competition is a reality for sterile fish too!

PowerPoint Presentation:

Polyploidy Polyploidy has been well-studied in fish and shellfish. Channel catfish triploids become larger than diploids Triploids converted feed more efficiently than diploids (Wolters et al., 1982), had six percent greater carcass yield at three years of age.

PowerPoint Presentation:

Intersexed fish Hermaphrodites-contain ovotestes, can go either way... MT treatment female after sex determination occurs (ovary has already started to develop) intersexed fish must be killed to determine if the process work! Not very good for aquaculture?

PowerPoint Presentation:

Hormonal regulation of sex differentiation Genotypic: “Master” gene (e.g., dmy), minor sex determining genes, autosomal genes Environmental factor (e.g., temperature) Sex determination ER Estrogen-regulated genes AR Androgen-regulated genes sf1, sox, foxl2, fig α Ovarian differentiation Testis differentiation Aromatase dmrt1 Bipotential gonad Estrogen Germ cell proliferation Entry into meiosis Mitotic arrest Proliferation Androgen 11 β -hydroxylase amh, sox9 Sex differentiation Female Male Part 1: Summary of the Problem and General Scientific Principles Sex differentatiation involves similar or the same players across vertebrates, with the steroidogenic enzyme aromatase and the transcription factor dmrt1 playing a central role

authorStream Live Help