What is the relationship between any two strands of DNA?

a. An A base on one always pairs with a G base on the other.


b. One was the template for the synthesis of the other.


c. They are a pair of sister chromatids.


d. They are connected to each other by sugar-phosphate bonds.


e. They have identical base sequences.

What is the relationship between any two strands of DNA?
Not the best-worded question. I assume the question is referring to the two complementary strands of a naturally ocurring, double-stranded DNA molecule. (I.e., not literally *any* two strands of DNA.)





In that case, I think the answer they want is b.





Not d, because the two strand are not connected "to each other" by sugar-phosphate bonds. Those hold each individual strand together, but don't connect the two strands together.





b is correct because under ordinary circumstances, new DNA is formed by semi-conservative replication of pre-existing DNA. That means you take some double stranded DNA, separate the two strands, and then use each separate strand as a template to make a new complementary strand.





Thus, for any dsDNA you'd normally find in a cell, one strand would have served as the template for the synthesis of the other - b.
Reply:d
Reply:d. They are connected to each other by sugar-phosphate bonds.





a is wrong because A pairs with T, b is wrong because two DNA strands are not necessarily based off of each other, (and likewise for c), and e is definitely not true. Otherwise, we wouldn't have variety.