Evolution and Genetic Engineering - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 695

14.7.2. Gram-Positive Bacteria 726 14.8. Regulatory Constraints on

Genetic Processes 14.7.3. Lower Eukaryotic Cells 726 733

14.7.4. Mammalian Cells 727

14.9. Metabolic Engineering 736

14.7.5. Insect Cell-Baculovirus
System 729 14.10. Protein Engineering 738

14.7.6. Transgenic Animals 731

14.11. Summary 739

14.7.7. Transgenic Plants and Plant
Cell Culture 731 Problems 740

14.7.8. Comparison of Strategies 732

Living organisms (unicellular and multicellular; prokaryotic or eukaryotic) utilize nucleic
acids (deoxyribonucleic acid or DNA and ribonucleic acid or RNA) for transferring genetic
information from one generation to the next and also to decode genetic information into
messenger molecules (from DNA to RNA) and then to effecter molecules (proteins), as we
have learned in Chapter 10. All prokaryotic and eukaryotic cells/organisms use DNA as their
genetic material. Some viruses (called retroviruses), like HIV, use messenger RNA (mRNA)
for transferring genetic information to their next generation. To transfer genetic information,
DNA is replicated into an exact copy and is passed on to the next generation of cells/organ-
isms. If the genetic material is RNA (usually mRNA), it is first converted to DNA (through
reverse transcription); copies of RNA are generated from this DNA, and are then passed
on to the next generation. In the passing of genetic information, errors can occur. Despite
active self-repairs, some mistakes can carry to the next generation. Some individuals can
receive additional genetic information through natural or artificial means. Organisms evolve
via genetic mistakes and accidental acquiring of foreign genes as selected by the environ-
ment. Therefore, genetic information can be manipulated to produce new cells/organisms
with a purpose, which leads to genetic engineering.
To create effecter molecules (proteins) from genetic code (DNA), DNA is first transcribed
into messenger RNA and then this message is translated into a protein molecule (Central
Dogma of biology). We start the discussions from the passing of genetic information to the
next generation and their potential errors.

14.1. MUTATIONS

Although the cell has a well-developed system to prevent errors in DNA replication and
an active repair system to correct damage to a DNAmolecule, mistakes occur. These mistakes
are called mutations. The genetic contents (DNA or RNA) of a cell/organism are called its
genotype, and the characteristics that are expressed by the organism (by virtue of its geno-
type) is called phenotype.
The alterations in the genotype of a cell/organism are called mutations and the altered
phenotype (consequent to the alterations in genotype) is called a mutant. The majority of
phenotypic changes in response to environmental factors (e.g. darkening of human skin after
exposed to sunlight or tanning) are reversible and are produced by the already existing geno-
typic structure or mechanisms. On the other hand, the phenotypic changes that occur as