Concept 13.1 Recombinant DNA Can Be Made in the Laboratory

• Biotechnology is the use of living cells to make or modify materials and processes useful to people.
   
• Restriction enzymes make cuts in double-stranded DNA, creating fragments of various lengths.
   
• DNA fragments can be separated by size using gel electrophoresis. Review Figure 13.2 and ANIMATED TUTORIAL 13.1
   
• DNA fragments from different sources can be used to create recombinant DNA by splicing them together using DNA ligase. Review Figures 13.3 and 13.4 and WORKING WITH DATA 13.1
   

Concept 13.2 DNA Can Genetically Transform Cells and Organisms

• One goal of recombinant DNA technology is to clone a particular gene, either for analysis or to produce its protein product in quantity.
   
• Bacteria, yeasts, and cultured plant and animal cells are commonly used as hosts for recombinant DNA. The insertion of foreign DNA into host cells is called transformation, or if the host cells are derived from an animal, transfection.
   
• Various methods are used to get recombinant DNA into cells. These include chemical and physical treatments for plasmids and the use of viral vectors.
   
• Selectable markers such as genes for antibiotic resistance are used to select for host cells that have taken up a foreign gene. Review Figure 13.5
   
• Reporter genes (of which selectable markers are one type) are genetic markers with easily identifiable phenotypes. Review Figure 13.6
   

Concept 13.3 Genes and Gene Expression Can Be Manipulated

• DNA fragments from a genome can be inserted into host cells to create a genomic library. A cDNA library is made by reverse transcribing mRNA to make cDNA. Review Figure 13.7
   
• Synthetic DNA containing any desired sequence can be made in the laboratory.
   
• Manipulating gene expression is one way to study the functions of particular genes.
   
• Homologous recombination is used to knock out a gene in a living organism. Review Figure 13.8
   
• Gene silencing techniques using antisense RNA or siRNA are used to prevent the translation of genes. Review Figure 13.9
   
• DNA microarray technology permits the screening of thousands of cDNA sequences at the same time. Review Figure 13.10 and ANIMATED TUTORIAL 13.2
   

Concept 13.4 Biotechnology Has Wide Applications

• Expression vectors allow transgenes to be expressed in host cells. Review Figure 13.11 and WEB ACTIVITY 13.1
   
• Recombinant DNA techniques have been used to make medically useful proteins. Review Figure 13.12
   
• Pharming is the use of transgenic plants or animals to produce pharmaceuticals. Review Figure 13.13
   
• Transgenic crop plants can be adapted to their environments, rather than vice versa. Review Figure 13.16
   
• There is public concern about the application of recombinant DNA technology to food production.