Restriction Endonucleases

Question 1

True or false: Type II restriction enzymes are considered of little value in molecular biology. Only Type I restriction enzymes can be used as specific cutting tools.

Answer 1

False

Question 2

According to standard naming for restriction enzymes, an enzyme from Grampositivobacter skinius Strain X would be called:

Answer 2

GskX I

Question 3

Restriction endonucleases cut DNA molecules:

Answer 3

Internally

Question 4

Type II restriction enzymes are useful biotechnology tools for all of the following reasons, except:

Answer 4

They can cut one of the two strands of the double helix

Question 5

The fourth restriction endonuclease isolated from the bacterium Nonamarea recticatens is called:

Answer 5

NreIV

Question 6

True or false: single-stranded tails produced across double-stranded DNA by a restriction endonuclease can also be referred to as overhangs.

Answer 6

True

Question 7

Type I and Type II restriction enzymes (REs) differ in that:

Answer 7

Type I enzymes cut 1,000 base pairs away from the sequence they recognise, whereas Type II cut within the recognition sequence

Question 8

The recognition site for the restriction endonuclease Styl is CCWWGG. The substrate sequences are therefore:

Answer 8

CCTAGG and CCATGG

Question 9

True or false: the recognition sequence of a restriction endonuclease cannot be found on the bacterium’s own genome.

Answer 9

False

Question 10

The optimal buffer for all restriction digestions:

Answer 10

Will vary depending upon the restriction enzyme used.

Question 11

The restriction endonuclease MlsII recognises the sequence 5’GCTTAAGC3’. If human DNA was digested with this enzyme, statistically, how often would the recognition sequence be likely to be found?

Answer 11

Once per 74764 bases

Question 12

The enzyme AvaII recognises the sequence GGTCC. However, it is sensitive to methylation at its 5’ end. It will therefore not cut if methylation occurs in which of the following sequences:

Answer 12

…CGGTCCT…

Question 13

The volume of stock restriction enzyme to use in a restriction digestion tube should always compose:

Answer 13

10% or less of the final reaction volume

Question 14

Based on their recognition sequences and their cut sites, BamHI and BgIII are examples of:

Question 14

Based on their recognition sequences and their cut sites, BamHI and BgIII are examples of:

Answer 14

Isocaudamers

Question 15

If one DNA strand has the sequence 5’ ATTCGGCTTC 3’, the complementary DNA strand would have the sequence:

Answer 15

5’ GAAGCCGAAT 3’

Question 16

Under non-optimal conditions, restriction enzymes can cleave sequences that are similar to, but not, the target site. This phenomenon is often referred to as:

Answer 16

Star activity

Question 17

Restriction endonucleases that share the same recognition sequence, but cleave DNA at a different site within that sequence are called:

Answer 17

Neoschizomers

Question 18

The optimal temperature for all restriction digestions:

Answer 18

Will vary depending on the restriction enzyme used

Question 19

In double-stranded DNA, which base ratio always equals one?

Answer 19

(A+G)/(C+T)

Question 20

The correct addition of reagents to a digestion reaction is:

Answer 20

Water, buffer, DNA, enzyme

Question 21

What do the letters Y and R represent in this recognition sequence for the restriction endonuclease SmII?

Answer 21

Pyrimidine and purine