Question

DNA fragments with sticky ends are not allowed to undergo self-ligation by:
A. Unwindase
B. Single strand binding proteins
C. Gyrase
D. Alkaline phosphatase

Answer 1

Hint: DNA fragmentation is the breaking or separation of DNA strands into pieces. It can be performed intentionally by laboratory workers or by cells or can take place spontaneously. Spontaneous or accidental DNA fragmentation is fragmentation that gradually accumulates in a cell. The blunt or sticky ends refer to the characteristics of the end of DNA molecules, which are commonly produced by restriction enzymes that cut the DNA.

Complete Step-by-step answer:
DNA fragments cut by restriction enzymes are referred to as restriction fragments. They can be divided by gel electrophoresis.
Restriction enzymes can produce fragments with sticky ends. The single-stranded free ends that project from each fragment of DNA duplex are unpaired bases and are called "sticky ends".
Sticky ends can join with the same complementary ends of DNA fragments from some other sources. DNA fragments with sticky ends are not allowed to endure self-ligation by Alkaline phosphatase. Self-ligation is a common undesirable result of a ligation reaction. 
Alkaline phosphatase is a very useful enzyme in genetic engineering, it takes away the 5′phosphate group from DNA and RNA fragments. It also eliminates the 5′ phosphate groups from nucleotides and proteins.
Therefore the correct answer is Option D.
Note: DNA fragments are made up of molecules known as a nucleotide. Each nucleotide is comprised of a phosphate group, a sugar group, and a nitrogen base. A sticky end is a fragment of DNA generated by a staggering cut using restriction enzymes, where the terminal portion has a stretch of unpaired bases. Examples are Hind III, EcoR I, BamH I, etc.