Lecture 28 Flashcards
What is gene transfer?
Movement of genes between orgainsms
What is a transgene?
The new gene introduced into the transgenic organism
What is an transgenic organism?
The result of gene transfer
What is transformation
The process of gene transfer (or conversion of cultured mammalian cells to a cancerous/immortal state outside of this course)
What is gene therapy?
gene transfer aimed at correction of a genetic defect but not targeting the germ line
Why is gene transfer easier to do in plants?
Almost all cells are totipotent so any cell type can be used
What single animal cells can be used for gene transfer?
Fertilized egg cells
Embryonic stem cell lines (mice)
Construction of a transgenic cell line and then perform a nuclear transplant into an egg cell
Why is plant gene transfer easier to perform?
totipotency of all cells and agrobacterium
What is agrobacterium tumefaciens?
A bacteria that can infect plants at wound sites
It is a natural genetic engineer as it has T-DNA on a tumour inducing plasmid
What are the features of the tumour inducing plasmid of agrobacterium tumefaciens?
Contains genes for auxin and cytokinin
There T genes which are the virulence factor of the bacteria and are only expressed in the plant
Also contains genes for nopaline synthesis (which is a type of opinine sugar bound to amino acids) and genes for the use of nopaline as a source of nitrogen
How are agrobacterium vectors constructed?
The normal T genes are replaced with the desired genes and a kanamycin resistance gene inserted between border repeats of 20 bases, often an artificial T-DNA is cloned onto a smaller second plasmid to make it easier to manipulate
What are the features of agrobacterium based gene transfer?
It is simple, cheap and easy to perform
introduces single segment of DNA
Random insertion site (but genes are preferred)
High efficiency for many plants
However has the drawback of needing regeneration from cells within cultured explant and host range limited for gene transfer process
What is the upshot of agrobacterium gene transfer?
Does not work for all species as there is a much lower frequency for many monocots and does also not work for all varieties of a species equally
What is biolistics?
A method where DNA is introduced into plant cells via particle bombardment
These particles penetrate only the top 2 layers of cells
What are the features of biolistics?
It is host range independent Can be used on animals and microbes Triggers more DNA rearrangements Is successful with moderate frequency Produces a high copy number
What are the advantages of ‘roundup ready’ crops?
There is a cost reduction as it it is cheaper and easier for the farmer and a gain in profit as the company can sell both the seeds and the herbicide
There are environmental advantages as less herbicide can be used and promotes no-till agriculture
What are the disadvantages of ‘round-up ready’ crops?
There are higher circulating herbicide concentrations in plants with some resistance occurring in weeds
What are the applications of transgenic sheep and cattle?
Milk is a good source of high yield clean protein, it could be possible to cause protein over production
What is possibly the most important application of transgenic animals?
Can be used to produce knockout mice which can provide important insight into the genetic basis of disease
What is the stance of gene transfer in humans?
Germ line transformation is banned
Gene therapy can be performed in somatic cells only, designed to correct a genetic defect in a patient but be non-heritable
Has been attempted in patients with ADA and Cancer, largely these results have been disappointing with rare long term effects however there is still extensive research
