Genetic requirement for transgenic fish development

Group members Rameen 25Hina 4Syeda iqra 5Mahnoor 2Maleeha 6

Date : 17th may 2016

An organism that has a foreign or modified gene transferred to its genome using the in vitro genetic techniques is called a genetically modified organism (GMO) or a transgenic organism.

Transgenes can originate from phylogenetically distant organisms or from the same species.

First transgene fish was developed in 1980’s. For the production of transgenic animal, a cloned

gene is transferred into the fertilized egg before the completion of first cleavage.

Scientists are seeking ways to genetically engineer fish and other seafood species to introduce or amplify economically valuable traits.

Fish are of particular interest to researchers since many fish produce large quantities of eggs; those eggs, being external to the animal, make it relatively simple to insert novel DNA

Research on transgenic fish is currently under development for at least 35 species of fish worldwide, as well as for a variety of mollusks, crustaceans, plants, and marine microorganisms, for various purposes.

Uses: Transgenic technology has been successfully used to

develop fast-growing super-fish stocks for human consumption to produce pharmaceuticals to test water contamination in both developed and

developing countries. Several laboratories now have GM fish with increased

growth performance caused by extra copies of GH genes (growth hormones genes)

A. Selection of species and genes For the aquacultural importance, Common

carp, Channel catfish, Chinese carps, Salmon, Trout and Tilapia are the best species for the transgenic project.

Improvement of growth rate, imparting disease and environmental stress resistance are some important traits for transgenesis.

B. Reporter genes a gene whose products detects or marks the cells,

tissues, organisms that express the gene from those that do not. used as an indication of whether a certain gene has been taken up by or expressed in the cell or organism population.

Reporter genes isolated from prokaryotes, E. coli, are used in fishes- ie lac Z gene, Cat gene .

Recently luciferase and green fluorescent protein are used.

Ornamental GloFish have different fluorescent colors. They are available as a pet

GloFish

C. Genes of interest

1. Growth hormone gene ‘Growth hormone’ (GH) is produced by the anterior

lobe of the pituitary plays the key role. It increases growth by stimulating, appetite and

cell reproduction protein hormone molecular weight of about 22 kD Transgenic fish carrying GH gene will produce

growth hormone endogenously bypassing the necessity of exogenous hormone treatment.

GH gene has been cloned in some fishes either from the genomic library or from the cDNA library.

Salmon/trout can grow up to 6 times faster than wild-type fish because they have extra copies of Growth Hormone (GH) gene.

2. Antifreeze protein genes Production of cold resistant fish variety is useful for

establishing aquaculture industry in the temperate region, where water gets frozen during winter.

The gene responsible for imparting cold resistance was cloned from winter flounder (Pseudopleuronectes americanus), which lives in the polar sea.

This species avoids freezing of its blood even at –7C temperatures by producing a set of anti-freeze proteins (AFP).

AFP are produced in the liver and exported to the blood stream.

C. Genes of interest

3. Disease resistanceFish has poorly developed antibody dependent immunity. Efforts to produce disease resistance in fish stocks by transgenesis have begun recently.The potential of Rainbow trout lysozyme gene as a bacterial inhibitor was assessed in Atlantic salmon.

C. Genes of interest

E. Detection of transgene

There are various ways and means to detect this. Most of them used southern blot and northern blot

to detect the transgenes using a suitable probe.

Food safety of transgenic (GM) fish

GM food safety depends on the nature of the gene, the transgene product it encodes and the resulting phenotype.

Transgenic fish have received extra copies of GH genes, resulting in only moderately raised levels of circulating GH.

GH is a protein hormone which is degraded along with all other food protein.

Meat from fish modified with GH is regarded as completely safe for human consumption

Concerns have been voiced of the possible risks of consumption of transgenes,

their resulting protein, potential production of toxins by aquatic

transgenic organisms, changes in the nutritional composition of

foods.

Environmental impact of transgenic fish The possible impacts from the escape of GM

organisms from aquaculture facilities are of great concern to some scientists and environmental groups.

Escaped transgenic fish could harm wild fish through increased competition or predation.

The consequences of such competition would depend on many factors, including the size of the wild population, the number and specific genetic strain of the escaped fish, and local environmental conditions.