Chapter 9.1: Fragmenting DNA

Question 1

What is digestion?

Answer 1

the act of a restriction enzyme cutting is often called digestion

Question 2

How does size of DNA affect size traveled during electrophoresis?

Answer 2

o With linear DNA molecules, differences in size are proportional to differences in length: the longer the molecule, the larger the volume it occupies as a random coil
 In any given period of electrophoresis, smaller DNAs will travel greater distances from the wells than larger DNAs

Question 3

What is the function of a restriction enzyme?

Answer 3

o A restriction enzyme recognizes a specific sequence of bases anywhere within the genome and then severs two phosphodiester bonds at that sequence, one in the sugar-phosphate backbone of each strand

Question 4

What is the size of recognition sites?

Answer 4

o Recognition sites/fragments are every 4n, where n is the number of bases in the site

Question 5

Define sticky ends

Answer 5

 Displaced equally in opposite directions from the line of symmetry but one or more bases to generate fragments with single-stranded ends
• Referred to as sticky ends because they are free to base pair with a complementary sequence from the DNA of any organisms cut by the same restriction enzyme

Question 6

What causes different linear DNA molecules to migrate at different speeds during electrophoresis?

Answer 6

o Only differences in size cause different linear DNA molecules to migrate at different speeds during electrophoresis

Question 7

What is a restriction fragment?

Answer 7

 The fragments generated by restriction enzymes are referred to as restriction fragments

Question 8

Define electrophoresis

Answer 8

o To analyze the DNA in a sample, biologists employ a technique called electrophoresis, the movement of charged molecules in an electric field

Question 9

Define blunt ends

Answer 9

 Straight through both DNA strands right at the line of symmetry to produce fragments with blunt ends