Lecture 28

Question 1

What is gene transfer?

Answer 1

Movement of genes between orgainsms

Question 2

What is a transgene?

Answer 2

The new gene introduced into the transgenic organism

Question 3

What is an transgenic organism?

Answer 3

The result of gene transfer

Question 4

What is transformation

Answer 4

The process of gene transfer (or conversion of cultured mammalian cells to a cancerous/immortal state outside of this course)

Question 5

What is gene therapy?

Answer 5

gene transfer aimed at correction of a genetic defect but not targeting the germ line

Question 6

Why is gene transfer easier to do in plants?

Answer 6

Almost all cells are totipotent so any cell type can be used

Question 7

What single animal cells can be used for gene transfer?

Answer 7

Fertilized egg cells
Embryonic stem cell lines (mice)
Construction of a transgenic cell line and then perform a nuclear transplant into an egg cell

Question 8

Why is plant gene transfer easier to perform?

Answer 8

totipotency of all cells and agrobacterium

Question 9

What is agrobacterium tumefaciens?

Answer 9

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

Question 10

What are the features of the tumour inducing plasmid of agrobacterium tumefaciens?

Answer 10

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

Question 11

How are agrobacterium vectors constructed?

Answer 11

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

Question 12

What are the features of agrobacterium based gene transfer?

Answer 12

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

Question 13

What is the upshot of agrobacterium gene transfer?

Answer 13

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

Question 14

What is biolistics?

Answer 14

A method where DNA is introduced into plant cells via particle bombardment
These particles penetrate only the top 2 layers of cells

Question 15

What are the features of biolistics?

Answer 15

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

Question 16

What are the advantages of ‘roundup ready’ crops?

Answer 16

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

Question 17

What are the disadvantages of ‘round-up ready’ crops?

Answer 17

There are higher circulating herbicide concentrations in plants with some resistance occurring in weeds

Question 18

What are the applications of transgenic sheep and cattle?

Answer 18

Milk is a good source of high yield clean protein, it could be possible to cause protein over production

Question 19

What is possibly the most important application of transgenic animals?

Answer 19

Can be used to produce knockout mice which can provide important insight into the genetic basis of disease

Question 20

What is the stance of gene transfer in humans?

Answer 20

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