is supported by many people and organizations, there are also some who oppose
the technology. Considering their possible motivations and potential biases,
discuss some of the reasons that groups have come out in favor or in opposition to
Golden Rice.- What are the potential benefits of producing pharmaceutical proteins in plants? What
are some of the disadvantages or potential dangers? - Animal genes can be inserted into plants and expressed. Would you be opposed to
eating foods from plants expressing proteins encoded by animal genes? By human
genes? Discuss the reasons for your answers.
8.1 Introduction
As discussed in Chapter 6, the specific order of the nucleotide bases of DNA determines the
function that a given sequence encodes. However, those four DNA bases are contained in a
repetitious sugar–phosphate backbone that is essentially identical in DNA from any source.
Because of this similarity of DNA structure in all organisms, there are no chemical limits on
DNA from any organism being transferable to another, and this has allowed the develop-
ment of transgenic plants carrying genes from many different sources, including microbes,
insects, and animals, including humans. Essentially, sources for transgenes are as deep as
our genomic knowledge in all of biology.
Many important traits in agriculture, such as crop yield, are often controlled by the action
of multiple genes working together. However, other useful traits can be controlled by just
a single gene. Because it has been easier to identify single-gene traits and produce trans-
genic plants with a limited number of introduced genes, most transgenic plants being
grown today originated via the transfer of just one or a few foreign genes. In this chapter
some of the most common genes and traits that have been engineered into transgenic
crops will be discussed, and we will also take a look into the future to some potential
applications of transgenic plants that could benefit consumers by providing improved
foods and products.
8.2 Identifying Genes of Interest via Genomic Studies
Advances in technologies used to determine DNA sequence and mRNA accumulation have
allowed detailed inquiry into the impressive quantities of information contained in the
genome of an organism.Genomicsis a broadly defined term, but it generally refers to a
strategy of using high-throughput, large-scale molecular techniques to analyze DNA
sequence or gene expression patterns.
Deciphering and interpreting the vast information of a genome sequence are the focus of
great efforts, and it is hoped that this information will lead to development of new tools for
crop improvement. In most crop species, this is a difficult task. For example, the soybean
genome consists of around 1.1 billion base pairs (bp) of DNA, whereas the maize genome is
considerably larger, at approximately 2.4 billion bp. For comparison, the size of the human
genome is slightly over 3 billion bp. These billions of base pairs of sequence are filled with
many regions that are highly repetitive, and many others that do not seem to encode for any
protein products. Identifying the important regions of plant DNA and those that contribute
to useful traits for farmers can require a combination of traditional breeding techniques,
194 GENES AND TRAITS OF INTEREST FOR TRANSGENIC PLANTS