KEY CONCEPT Biotechnology relies on cutting DNA at specific places.

1. KEY CONCEPT Biotechnology relies on cutting DNA at specific places.

2. Scientists use several techniques to manipulate DNA. • Chemicals, computers, and bacteria are used to work with DNA. • Scientists use these tools in genetics research and biotechnology.

3. Restriction enzymes cut DNA. • Restriction enzymes act as “molecular scissors.” • come from various types of bacteria • allow scientists to more easily study and manipulate genes • cut DNA at a specific nucleotide sequence called a restriction site

4. Different restriction enzymes cut DNA in different ways. • each enzyme has a different restriction site

5. Sticky vs. Blunt ends • Sticky ends result from cuts at palindromic sequences • Blunt ends results from cuts at non-palindromic sequences • Palindrome or no? • GATC • GACT

6. some cut straight across and leave “blunt ends” • some make staggered cuts and leave “sticky ends”

7. How are restriction enzymes named? • An enzyme Thermus aquaticus is used to cut DNA. It was the first restriction enzyme isolated from the bacterium. What is the name of the endonuclease? First letter represents first letter of genus The second two letters come from the first two letters of the bacterium’s species descriptor The first three letters are italicized because they are part of the bacterium’s scientific name A fourth letter represents the particular strain of bacteria A Roman numeral reveals the order in which an enzyme was discovered in the bacterium

8. Endonuclease animation

9. Restriction maps show the lengths of DNA fragments. • Gel electrophoresis is used to separate DNA fragments by size. • A DNA sample is cut with restriction enzymes. • Electrical current pulls DNA fragments through a gel.

10. Smaller fragments move faster and travel farther than larger fragments. • Fragments of different sizes appear as bands on the gel.

11. Gel electrophoresis animation SDS-PAGE

12. A restriction map shows the lengths of DNA fragments between restriction sites. • only indicate size, not DNA sequence • useful in genetic engineering • used to study mutations