4A Enzymes that manipulate DNA

Match each of the following enzymes that manipulate DNA with their function.

• Polymerases

• Synthesise new molecules of DNA or RNA

• Endonucleases

• Join fragments of DNA or RNA

• Ligases

• Cut DNA

The region of DNA targeted by a restriction endonuclease is known as the:

• Recognition site

• Active site

• Allosteric site

• Binding site

Label the following diagram showing the possible outcomes when endonucleases cut a DNA molecule.

a

b

sticky ends

blunt ends

If a circular DNA molecule is cut with a particular endocnuclease for which it has three recogntion sites, how many fragments of DNA will be produced?

• 1

• 2

• 3

• 4

If a linear DNA molecule is cut with a particular endocnuclease for which it has three recogntion sites, how many fragments of DNA will be produced?

• 1

• 2

• 3

• 4

When ligases join fragments of nucleic acids together, they do this by catalysing the formation of:

• Hydrogen bonds

• Phosphodiester bonds

• Peptide bonds

A difference between ligases and endonucleases is:

• Ligases are specific, endonucleases are not

• Endonucleases are specific, ligases are not

• The action of endonucleases is reversible, the action of ligases is not.

• The action of ligases is reversible, the action of endonucleases is not.

Which of the following enzymes is used in the process of transcription?

• RNA polymerase

• DNA polymerase

• DNA ligase

• Restriction endonucleases

In which direction do polymerases synthesise a complementary strand of nucleic acid?

• 5' to 3'

• 3' to 5'

• They can synthesise in either direction