Final answer:
An intact, linear, double-stranded DNA and a partially double-stranded DNA can effectively serve as templates for DNA synthesis, with the double-stranded nature providing stability and proper structure for the enzymes involved in the replication process.
Step-by-step explanation:
The DNA molecules that could serve as an effective template for DNA synthesis are as follows: an intact, linear, double-stranded DNA because during DNA replication, enzymes work to unwind the double helix so that each strand can be used as a template. This process specifically involves semi-conservative replication, where each new DNA molecule consists of one original strand and one newly synthesized strand. The partially double-stranded DNA can also serve as a template because it contains regions of double helix that can be unwound and used for DNA replication.
Single-stranded, circular DNA could potentially serve as a template if it were able to be stabilized and presented in a way that DNA polymerase can access it to synthesize the complementary strand. However, in most organisms, DNA replication typically involves double-stranded templates.
Elongation in DNA Synthesis
DNA synthesis elongation involves attaching complementary nucleotides to the template strand. The necessary unwinding of the DNA helix and pulling apart of the strands is performed by various proteins such as helicase before elongation occurs.