Cambridge International A Level Biology Revision Guide

Chapter 19: Genetic technology
Genes for the production
of carotene were extracted
from maize and the
bacterium Pantonoea
ananatis.
These genes, together with
promoters, were inserted into
plasmids.
The plasmids were inserted into
bacteria called Agrobacterium
tumefaciens.
These bacteria naturally
infect plants and so could
introduce the genetically
modified plasmid into rice
cells. They were mixed with
rice embryos in Petri dishes,
some of which were infected
by the bacteria carrying the
carotene genes.
The rice embryos, now
containing the carotene genes,
were grown into adult plants.
They produced seeds
containing carotene in
their endosperm.
Figure 19.22 Pro-vitamin A enhanced rice was engineered
using genes from the maize and a bacterium.
Figure 19.23 Normal rice on the left; Golden Rice on
the right.
research was carried out. The genetically modified rice is
called Golden Rice, because it contains a lot of the orange
pigment carotene (Figure 19.23).
The genetically modified rice is being bred into other
varieties of rice to produce varieties that grow well in
the conditions in different parts of the world, with the
same yield, pest resistance and eating qualities as the
original varieties. For example, the International Rice
Research Institute (IRRI) has worked with researchers
in Bangladesh to produce a pro-vitamin A enhanced
('Golden') variety of Bangladesh’s most popular rice
variety. Research with children in China has shown that
Golden Rice may be as useful as a source of vitamin
A from vitamin A capsules, eggs, or milk to overcome
vitamin A deficiency in rice-consuming populations.
There has been quite a lot of controversy over Golden
Rice. Several non-governmental organisations, opposed
to the use of genetic engineering in any crops, have
condemned Golden Rice as being the wrong way to solve
the problem of people eating diets that are short of
vitamin A. One of their arguments is that the main reason
that people eat diets that are short of vitamin A is poverty,
and that the way to solve the problem is to help them out
of poverty so that they have access to a more varied diet.
Others say that, although it would be better if we could
somehow lift these people out of poverty, this cannot be
quickly achieved.
Despite the research, development and evaluation of
Golden Rice that has taken place over the last ten years, it is
not yet available to farmers and consumers because it has to
be approved by national authorities in each country first.
With the help of the scientists who initially donated
their technology invention, an international network of
public sector rice research institutes and funding from
bodies such as the Bill and Melinda Gates Foundation,
Golden Rice seed will made available in developing
countries at no greater cost than white rice seed. Everyone
agrees that we need to solve the root causes of poor diets –
which include numerous political, cultural and economic
issues – but, meanwhile, pro-vitamin A enhanced rice
could help millions of people to avoid blindness or death.
QUESTION
19.11 a Explain why promoters were inserted into the
plasmids (Figure 19.22).
b In the production of bacteria that synthesise
human insulin (page 467), plasmids acted
as vectors to introduce the gene into the
bacterial cells. What were the vectors used in
the production of vitamin A enhanced rice?
Explain your answer.
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