15. Manipulating Genes In Organisms Flashcards
What barriers did scientists face in gene transfer?
🔹 genes are normally transferred from parent to offspring and remain within the species.
🔹 transfer of genes between species under natural conditions is not possible due to the species barrier, members of different species cannot mate and gametes of different species cannot fuse together.
GMOs definition
Organisms whose genome contain heritable changes created through the use of genetic engineering technology
Examples of gene alteration
The addition of a gene or a segment of DNA
Switching genes on or off
The silencing of a gene so that its function is lost
A foreign gene or DNA segment is added to the genome
Transgenic organisms
Organisms that carry in their genomes one or more genes artificially introduced from another species
Mice micro injection
DESCRIPTION
🔹 DNA of the gene concerned is injected into the fertilised egg of a mouse at a stage when the male and female pronuclei have not yet fused. Produces some mouse eggs with one or more copies of injected DNA that has randomly integrated into their genomes.
🔹 a number of eggs are implanted in a surrogate female mouse, and life mouse pups will be born 19 days later.
PURPOSE
🔹 DNA micro injection of eggs is used when the aim is to add a gene to create Gm mice (eg. Human growth hormone)
Mice embryonic stem cells
DESCRIPTION
🔹 Silencing of a gene is achieved by creating a gene that is homologous to the target gene but which carries a defect in its base sequence that makes it non functional.
🔹 This defective DNA sequence is injected into an embryonic stem cell and in some cells the defective gene replaces the functional target gene by recombination.
🔹 The target gene in those cells is silenced or knocked out
PURPOSE
🔹 To silence or disable a specific target gene in order to identify its function by seeing what happens when the gene is inactivated.
Atlantic salmon
DESCRIPTION
🔹 First GM animal approved for human consumption. It has growth hormone gene from a chinook salmon, a promoter gene and terminator sequence from ocean pout (an eel like fish).
🔹 To avoid interbreeding with native species the eggs are made sterile.
PURPOSE
🔹 To create salmon that can reach maturity in a shorter time frame. It is estimated that the time to market was reduced from three years to 18 months.
Hamsters
DESCRIPTION
🔹 The production of human recFSH occurs in transgenic hamster cells. These cells have been genetically engineered so that they contain the human gene that controls production of FSH.
🔹 recFSH is made in larger quantities, it’s supply more reliable and pure than urine derived product.
PURPOSE
🔹 Recombinant FSH is made available to women who cannot produce their own FSH
Goats and cows
DESCRIPTION
🔹 Some research has involved the production of transgenic cows and goats whose cells carry human genes for specific protein products.
🔹 If these genes are expressed in the milk produced by these transgenic mammals, they function as mini pharmaceutical factories to produce particular protein products
PURPOSE
🔹 Cows produce human protein, serum albumin
🔹 Goats produce protein which prevents blood clotting used in heart surgery.
Agrobacterium mediated uptake of DNA
🔹 In nature these bacteria infect plants by inserting their ti plasmid into plant cells where a segment of the bacterial DNA is transferred into the plant genome causing diseases such as crown gall disease.
🔹 Foreign DNA inserted into plasmid t-DNA region and bacteria modified to make them harmless and non tumour produced.
Ingard cotton
DESCRIPTION
🔹These cotton plants were genetically engineered to include the cry1Ac gene from bacterial species Bacillis thuringiensis. The cry1Ac gene encodes a protein, known as Bt that acts as an insecticide.
🔹 Bt insecticide is non toxic, has a narrow target range and is not a contact insecticide- must be ingested by caterpillars to take effect.
PURPOSE
🔹 Bt insecticides are highly effective against the leaf feeding larvae of the cotton bollworm, major pests of the crop
Roundup ready canola
DESCRIPTION
🔹 The gox gene, from the bacterial species ochrobacterium anthropic, was engineered into canola plants using agrobactium as a vector.
🔹 The gox gene encodes an enzyme that breaks down glyphosate, the active ingredient of roundup herbicide, into a harmless product.
PURPOSE
🔹 Spraying canola crops with this herbicide kills weeds and other plants that lack the gox gene but leaves Gm canola plants unaffected.
Gm tomatoes
DESCRIPTION
🔹 Genetic engineering of tomatoes involves silencing genes that are induced by the ripening hormone ethylene.
🔹 suppression of these genes using a technique known as RNA interference
Purpose
🔹 delay ripening, reduce the rate of softening and extend the shelf life of tomats
Blue carnations
Description
🔹 The production of a blue carnation involves silencing some genes involved in the biochemical pathway of pigment production using RNAi. It also involves the addition of genes from a pansy and an iris
Golden rice 2
Description
🔹 Genome of golden rice variety has been genetically engineered by insertion into the ride genome of two additional genes into the pathway for the biosynthesis of carotene and the addition of a promoters sequence that keeps the pathway active in the cells of the rice endosperm.
🔹 the genes added are PSY gene from daffodil which codes the enzyme phytoene synthase. Crti gene from soil bacterium which encodes the enzyme phytoene desaturase, catalyses multiple steps in the synthesis of carotenoids up to lycopene.
Purpose: provides beta carotene which can be converted to vitamin a. Lack of which is major cause of preventable blindness in children, death from infection.
