Question

Answer whether the following statement is TRUE or FALSE. If FALSE, rewrite the sentence to be TRUE. (15 pt)

A. Reproducible set of DNA fragments will be produced every time a restriction endonuclease digests a known piece of DNA.

B. Restriction nucleases recognize and cut specific sequences on single-stranded DNA.

C. The larger the genome of the organism from which a library is derived, the larger the fragments inserted into the vector will tend to be.

D. Ligation reactions by ligase occur most efficiently between DNA fragments that are cut by different restriction enzymes.

E. Northern blotting utilizes antibody probe to visualize RNAs separated by gel electrophoresis.

Answer 1

A) False; Restriction enzymes simply cut the DNA sequence at a designated plaindromic site. Production of reproducible fragments is dependent upon the DNA sequence that is being used. If the same sequence is cut by same restriction enzyme everytime, only then will it produce reproducible fragments.

B) True

C) False; Size of genome has no bearing on the length of restriction fragment. It is entirely dependant on the type of restriction enzyme used.

D) True; For the insertion of a DNA fragment into a plasmid vector, it is preferable to use two different restriction enzymes to digest the DNA so that different ends are generated. The two different ends can prevent the religation of the vector without any insert, and it also allows the fragment to be inserted in a directional manner.

E) False; Northern Blotting uses hybridization probe complementary to part of or the entire target RNA sequence