Nanette J. Pazdernik

DNA, RNA, and Protein

Two essential features of living creatures are the ability to reproduce their own genome and manufacture their own energy. To accomplish these feats, an organism must be able to make proteins using information encoded in its DNA. Proteins are essential for cellular architecture, giving the cell a particular shape and structure. Proteins include enzymes that catalyze reactions used to make energy. Proteins control cellular processes like replication. Proteins provide channels in the membrane for cells to communicate with each other or share metabolites. Making proteins is a key operation for all living organisms.

Inherited Defects and Gene Therapy

Genetic defects vary from trivial to life threatening. Although we tend to think of inherited conditions such as cystic fibrosis and muscular dystrophy as diseases, we often refer to cleft palates or color blindness as inherited defects. However, they are all due to mutations in DNA, the genetic material. Not only are some diseases directly caused by mutations, but susceptibility to infectious disease and to factors such as radiation also is influenced by a variety of genes. True human genetic engineering is still in the future. At present, genetic engineering is restricted to nonhumans and has resulted in the creation of transgenic plants and animals. Eugenics refers to deliberate improvement of the human race by selective breeding. Early eugenic proposals were based on choosing superior parents by visual inspection or medical screening and breeding them in much the same way as for prize pigs and pedigreed dogs. Today, we have reached the position where direct alterations of the human genome at the DNA level are technically feasible although still clumsy.

Basics of Biotechnology

Biotechnology involves the use of living organisms in industrial processes—particularly in agriculture, food processing, and medicine. Biotechnology has been around ever since humans began manipulating the natural environment to improve their food supply, housing, and health. Biotechnology is not limited to humankind. Beavers cut up trees to build homes. Elephants deliberately drink fermented fruit to get an alcohol buzz. People have been making wine, beer, cheese, and bread for centuries. For wine, the earliest evidence of wine production has been dated to c. 6000 BC. All these processes rely on microorganisms to modify the original ingredients. Ever since the beginning of human civilization, farmers have chosen higher yielding crops by trial and error, so that many modern crop plants have much larger fruit or seeds than their ancestors.

Aging and Apoptosis

Aging is a process we all start at birth and continue until death. Some people seem to age very gracefully, whereas others show signs of aging very early. Even ignoring the effects of infection or accident, quite a large range of life spans occurs among humans. Interestingly, there is a dramatic difference in the average life span of similar-sized mammalian species. For example, mice live about 2 to 3 years, whereas other rodents of similar size average about 5 to 10 years. Therefore, age is a relative term with differences within and between species.

From Cell Phones to Cyborgs

Several areas of biotechnology are advancing more rapidly than others. Perhaps the two most obvious are speedier DNA sequencing technology and emerging novel roles for RNA. This chapter is new to this edition of this book and tackles a third area. Unlike the other two, this area is on the boundary where biotechnology merges with computer science and electronics.

DNA Synthesis In Vivo and In Vitro

Replication copies the entire set of genomic DNA so that the cell can divide in two. During replication, the entire genome must be uncoiled and copied exactly. This elegant process occurs extremely fast in E. coli, where DNA polymerase copies about 1000 nucleotides per second. Although the process is slower in eukaryotes, DNA polymerase still copies 50 nucleotides per second. Many biotechnology applications use the principles and ideas behind replication; therefore, this chapter first introduces the basics of DNA replication as it occurs in the cell. We then review some of the most widely used techniques in genetic engineering and biotechnology, including chemical synthesis of DNA, polymerase chain reaction, and DNA sequencing.

RNA-Based Technologies

RNA plays a multifaceted role in biology that is adaptable for many different applications in biotechnology. The most widely understood role of RNA is in protein synthesis, which includes messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA) (see Chapter 2 ). However, RNA plays many other roles. Several small RNAs, such as snRNA, snoRNA, and gRNA, take part in RNA processing by removing introns. Some RNA sequences can catalyze enzyme reactions. Ribozymes, as they are called, are found in many organisms, catalyzing cleavage and ligation of various substrates. Between the increased speed and accuracy of sequencing and a heightened awareness of RNA in the cell, an ever-increasing number of roles has been found for RNA in the regulation of gene expression and in cell defense. Entirely new classes of noncoding RNAs (ncRNAs) have been discovered and characterized.

Transgenic Plants and Plant Biotechnology

One of the most promising fields within biotechnology is the development of transgenic plants. The ability to transfer genes from any organism into a plant unleashes a nearly boundless capacity to improve crops and other plants of interest. In this chapter, we explore the basis of this powerful and revolutionary technology.

Forensic Molecular Biology

DNA technology has many practical uses. Because every individual has a unique DNA sequence, DNA samples can be used for identification. The legal system is now using DNA evidence to determine guilt or innocence. The application of DNA technology began in Britain in the mid-1980s and appeared in America shortly afterward. Today many societies have reached the point of compiling DNA databases of known criminals—especially serious offenders. However, the most frequent use of DNA evidence is actually in cases of unknown or disputed paternity.

Chapter 19 – Cancer

Both inherited diseases and cancers are genetic in origin. Inherited diseases are genetic defects that are passed on from one individual to another via the germline. Mutations must occur in the germline cells, which give rise to the eggs and sperm, to be passed on to the descendants of a multicellular organism. In contrast, each occurrence of cancer is limited to a single multicellular organism and is not passed on to the next generation. If a mutation does occur in somatic cells—those making up the rest of the body—a variety of possibilities may result. A mutation that occurs early on in embryonic development may be highly detrimental, because each cell of the embryo gives rise to many cells during development. If the single precursor cell for a major organ or tissue suffers a serious mutation, the results may be serious or fatal. Most somatic mutations occurring later in development will affect only one or a few cells and will be of little major significance.