Question

What are sticky ends in DNA?

1) The 5' phosphates at the end of DNA molecules to which new nucleotides may be added
2) Blunt-ended DNA molecules that can be joined to other blunt ends, regardless of their origin
3) Single-stranded segments at the ends of DNA that can anneal with complementary sequences
4) The 3' hydroxyl (-OH) groups at the ends of DNA molecules to which new nucleotides may be added

Answer 1

Sticky ends in DNA are single-stranded segments at the ends of DNA that can anneal with complementary sequences, enabling the joining of DNA segments to create recombinant DNA. Option 3 is correct answer.

Step-by-step explanation:

What are Sticky Ends in DNA?

Sticky ends in DNA refer to single-stranded segments at the ends of DNA molecules that have been cut by restriction enzymes in a staggered manner. These sticky ends can form hydrogen bonds with complementary sequences of DNA that have been cut by the same enzyme, which allows for the two pieces of DNA to anneal or join together. The DNA molecule is composed of a sugar-phosphate backbone where the nucleotide bases stick out.

The phosphate group of one nucleotide bonds covalently with the sugar molecule of the next nucleotide, thereby forming this backbone. At the ends of this chain, you may find free phosphate groups at the 5' end or free hydroxyl groups at the 3' end, depending on how the DNA was cut. In the formation of recombinant DNA, sticky ends are crucial as they allow the combination of DNA fragments from different sources, facilitated by the enzyme DNA ligase, which seals the covalent bonds between the sugar and phosphate groups of the connecting fragments.

Given the multiple choice options provided within the question context, the correct answer to what sticky ends in DNA are is: Option 3 - Single-stranded segments at the ends of DNA that can anneal with complementary sequences.