The sticky ends of a fragmented DNA molecule are made up of
A. Calcium salts
B. Endonuclease
C. Unpaired bases
D. Methyl groups

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Hint: The sticky or blunt end of a fragmented DNA molecule depends on the enzyme which is used to cut the DNA

Complete answer:When both strands of DNA terminate in a base pair it is called blunt end whereas when these ends are created by various overhangs are called non blunt ends.
1. Non blunt ends are also called Sticky ends or cohesive ends when these overhangs are longer overhangs.
2. The stretch of unpaired nucleotides in the end of DNA is termed as overhang. These unpaired nucleotides are in either strands which create 3’ or 5’ overhangs.
3. There are two types of restriction enzymes viz, restriction endonucleases or exonucleases.
4. Restriction enzymes leave single stranded portions at the ends because it cuts the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands.
5. When the DNA is cut with a sticky end, it is most probably due to restriction of endonuclease enzymes.
6. When this enzyme cuts the pair of DNA strands it forms four base pairs, which create a four-base 5' overhang in one molecule and a complementary 5' overhang in the other.
7. These ends can be easily joined back together by a ligase.
8. Sticky ends form hydrogen bonds with their complementary cut counterparts hence the name, sticky ends.

Therefore, the correct answer is option C) Unpaired bases.

Note: When one cuts the vector and the source DNA with the same restriction enzyme, the recombinant vector molecule cannot be created.