Chapter 10 Glossary, Summary, and Practice Questions

KEY TERMS

anneal in molecular biology, the process by which two single strands of DNA hydrogen bond at complementary nucleotides to form a double-stranded molecule

biomarker an individual protein that is uniquely produced in a diseased state

biotechnology the use of artificial methods to modify the genetic material of living organisms or cells to produce novel compounds or to perform new functions

cloning the production of an exact copy—specifically, an exact genetic copy—of a gene, cell, or organism

gel electrophoresis a technique used to separate molecules on the basis of their ability to migrate through a semisolid gel in response to an electric current

gene therapy the technique used to cure heritable diseases by replacing mutant genes with good genes

genetic engineering alteration of the genetic makeup of an organism using the molecular methods of biotechnology

genetic map an outline of genes and their location on a chromosome that is based on recombination frequencies between markers

genetic testing identifying gene variants in an individual that may lead to a genetic disease in that individual

genetically modified organism (GMO) an organism whose genome has been artificially changed

genomics the study of entire genomes, including the complete set of genes, their nucleotide sequence and organization, and their interactions within a species and with other species

metagenomics the study of the collective genomes of multiple species that grow and interact in an environmental niche

model organism a species that is studied and used as a model to understand the biological processes in other species represented by the model organism

pharmacogenomics the study of drug interactions with the genome or proteome; also called toxicogenomics

physical map a representation of the physical distance between genes or genetic markers

plasmid a small circular molecule of DNA found in bacteria that replicates independently of the main bacterial chromosome; plasmids code for some important traits for bacteria and can be used as vectors to transport DNA into bacteria in genetic engineering applications

polymerase chain reaction (PCR) a technique used to make multiple copies of DNA

protein signature a set of over- or under-expressed proteins characteristic of cells in a particular diseased tissue

proteomics study of the function of proteomes

recombinant DNA a combination of DNA fragments generated by molecular cloning that does not exist in nature

recombinant protein a protein that is expressed from recombinant DNA molecules

reproductive cloning cloning of entire organisms

restriction enzyme an enzyme that recognizes a specific nucleotide sequence in DNA and cuts the DNA double strand at that recognition site, often with a staggered cut leaving short single strands or “sticky” ends

reverse genetics a form of genetic analysis that manipulates DNA to disrupt or affect the product of a gene to analyze the gene’s function

transgenic describing an organism that receives DNA from a different species

whole genome sequencing a process that determines the nucleotide sequence of an entire genome

CHAPTER SUMMARY

Cloning and Genetic Engineering

Nucleic acids can be isolated from cells for the purposes of further analysis by breaking open the cells and enzymatically destroying all other major macromolecules. Fragmented or whole chromosomes can be separated on the basis of size by gel electrophoresis. Short stretches of DNA can be amplified by PCR. DNA can be cut (and subsequently re-spliced together) using restriction enzymes. The molecular and cellular techniques of biotechnology allow researchers to genetically engineer organisms, modifying them to achieve desirable traits.

Cloning may involve cloning small DNA fragments (molecular cloning), or cloning entire organisms (reproductive cloning). In molecular cloning with bacteria, a desired DNA fragment is inserted into a bacterial plasmid using restriction enzymes and the plasmid is taken up by a bacterium, which will then express the foreign DNA. Using other techniques, foreign genes can be inserted into eukaryotic organisms. In each case, the organisms are called transgenic organisms. In reproductive cloning, a donor nucleus is put into an enucleated egg cell, which is then stimulated to divide and develop into an organism.

In reverse genetics methods, a gene is mutated or removed in some way to identify its effect on the phenotype of the whole organism as a way to determine its function.

Biotechnology in Medicine and Agriculture

Genetic testing is performed to identify disease-causing genes, and can be used to benefit affected individuals and their relatives who have not developed disease symptoms yet. Gene therapy—by which functioning genes are incorporated into the genomes of individuals with a non-functioning mutant gene—has the potential to cure heritable diseases. Transgenic organisms possess DNA from a different species, usually generated by molecular cloning techniques. Vaccines, antibiotics, and hormones are examples of products obtained by recombinant DNA technology. Transgenic animals have been created for experimental purposes and some are used to produce some human proteins.

Genes are inserted into plants, using plasmids in the bacterium Agrobacterium tumefaciens, which infects plants. Transgenic plants have been created to improve the characteristics of crop plants—for example, by giving them insect resistance by inserting a gene for a bacterial toxin.

Genomics and Proteomics

Genome mapping is similar to solving a big, complicated puzzle with pieces of information coming from laboratories all over the world. Genetic maps provide an outline for the location of genes within a genome, and they estimate the distance between genes and genetic markers on the basis of the recombination frequency during meiosis. Physical maps provide detailed information about the physical distance between the genes. The most detailed information is available through sequence mapping. Information from all mapping and sequencing sources is combined to study an entire genome.

Whole genome sequencing is the latest available resource to treat genetic diseases. Some doctors are using whole genome sequencing to save lives. Genomics has many industrial applications, including biofuel development, agriculture, pharmaceuticals, and pollution control.

Imagination is the only barrier to the applicability of genomics. Genomics is being applied to most fields of biology; it can be used for personalized medicine, prediction of disease risks at an individual level, the study of drug interactions before the conduction of clinical trials, and the study of microorganisms in the environment as opposed to the laboratory. It is also being applied to the generation of new biofuels, genealogical assessment using mitochondria, advances in forensic science, and improvements in agriculture.

Proteomics is the study of the entire set of proteins expressed by a given type of cell under certain environmental conditions. In a multicellular organism, different cell types will have different proteomes, and these will vary with changes in the environment. Unlike a genome, a proteome is dynamic and under constant flux, which makes it more complicated and more useful than the knowledge of genomes alone.

ART CONNECTION QUESTIONS

• Figure 10.7 Why was Dolly a Finn-Dorset and not a Scottish Blackface sheep?

REVIEW QUESTIONS

• In gel electrophoresis of DNA, the different bands in the final gel form because the DNA molecules .

• are from different organisms
• have different lengths
• have different nucleotide compositions
• have different genes
• In the reproductive cloning of an animal, the genome of the cloned individual comes from .
• a sperm cell
• an egg cell
• any gamete cell
• a body cell
• What carries a gene from one organism into a bacteria cell?
• a plasmid
• an electrophoresis gel
• a restriction enzyme
• polymerase chain reaction
• What is a genetically modified organism (GMO)?

• a plant with certain genes removed
• an organism with an artificially altered genome
• a hybrid organism
• any agricultural organism produced by breeding or biotechnology
• What is the role of Agrobacterium tumefaciens in the production of transgenic plants?

CRITICAL THINKING QUESTIONS

• What is the purpose and benefit of the polymerase chain reaction?
• Today, it is possible for a diabetic patient to purchase human insulin from a pharmacist. What technology makes this possible and why is it a benefit over how things used to be?

• Genes from A. tumefaciens are inserted into plant DNA to give the plant different traits.
• Transgenic plants have been given resistance to the pest A. tumefaciens.
• A. tumefaciens is used as a vector to move genes into plant cells.
• Plant genes are incorporated into the genome of

Agrobacterium tumefaciens.

• What is the most challenging issue facing genome sequencing?
• the inability to develop fast and accurate sequencing techniques
• the ethics of using information from genomes at the individual level
• the availability and stability of DNA
• all of the above
• Genomics can be used in agriculture to:
• generate new hybrid strains
• improve disease resistance
• improve yield
• all of the above
• What kind of diseases are studied using genome-wide association studies?
• viral diseases
• single-gene inherited diseases
• diseases caused by multiple genes
• diseases caused by environmental factors
• Describe two of the applications for genome mapping.
• Identify a possible advantage and a possible disadvantage of a genetic test that would identify genes in individuals that increase their probability of having Alzheimer’s disease later in life.