The 3' end of a DNA strand terminates with a sugar that has a free OH group on its 3' carbon. This end is complementary to the 5’ end of another DNA strand.
The 5' end of a DNA strand terminates in a phosphate group. This end is complementary to the 3’ end of another DNA strand.
DNA strands pair in an antiparallel manner, such that the 5' end of one DNA strand lines up with the 3' end of the paired strand.
Complementary strands pair, meaning that the nucleotide bases composing each strand must pair with the corresponding nucleotide base of the other strand. Thymine and adenine pair, while guanine and cytosine also pair with one another.
Thymine and adenine are two bases that form a pair. They are complementary bases that form hydrogen bonds, which hold DNA strands together.
The adenine-thymine base pair forms two hydrogen bonds.
In RNA, there is no thymine base. Instead, uracil is used. As a result, in RNA, adenine and uracil form a base pair with two hydrogen bonds.
Guanine and cytosine are the other two bases that form a pair, and they do so in both DNA and RNA.
The guanine and cytosine base pair bond consists of three hydrogen bonds, which makes G-C pairs stronger than T-A pairs.
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