Final answer:
Two single-stranded DNA molecules with complementary sequences can anneal through the formation of hydrogen bonds, forming a double-stranded DNA. This process is fundamental in molecular biology techniques like cloning and is influenced by the GC content of the DNA.
Step-by-step explanation:
When two single-stranded DNA molecules from different sources have complementary sequences, they can come together in a process known as annealing. This process occurs because of the formation of hydrogen bonds between the nucleotide base pairs of the two sequences. For instance, when DNA molecules feature complementary sticky ends, they can easily anneal at these ends. Sticky ends are created by the action of restriction enzymes and have overhangs that are complementary to each other. The annealing step is critical in molecular cloning and hybridization techniques, allowing the join of two DNA fragments from different sources to form a new recombinant DNA molecule. The DNA ligase enzyme then permanently joins these fragments, creating a continuous double-stranded DNA.
Moreover, this concept is at the core of biotechnological applications such as polymerase chain reaction (PCR) and the creation of recombinant DNA, like the groundbreaking work done by Paul Berg in 1972. It's essential to recognize that the GC content of DNA can affect the efficiency of denaturation and subsequent annealing, as the C-G base pair forms three hydrogen bonds, making it more stable and therefore more difficult to separate than the A-T base pair, which forms only two hydrogen bonds.