DNA and RNA Structure Quiz

Study Notes

DNA is comprised of deoxyribonucleotides, each containing deoxyribose sugar, a phosphate group, and a nitrogenous base.
Purines include adenine and guanine.
Pyrimidines include cytosine and thymine.
Thymine is unique to DNA.
Phosphodiester bonds form between the 5' carbon of one nucleotide and the 3' carbon of the next, creating a sugar-phosphate backbone.
The two strands of DNA are antiparallel - they run in opposite directions.
On the outside of the helix, a sugar-phosphate backbone is present, forming the “rungs” of the DNA helix ladder.
Hydrogen bonds form between complementary nitrogenous bases on the interior of DNA - adenine pairs with thymine, and cytosine pairs with guanine.

RNA contains ribose sugar, a phosphate group, and a nitrogenous base.
RNA contains uracil in place of thymine.
RNA is typically single-stranded, but can fold upon itself due to complementary base pairing.

DNA replication is the process by which DNA is copied.
It is semi-conservative, meaning each new DNA molecule contains one original strand and one newly synthesized strand.

The replication complex binds at the origin of replication, a specific base sequence.
Helicase unwinds DNA, and helix-destabilizing proteins help keep strands separated.
Replication starts at the replication fork.

The leading strand elongates continuously into the replication fork.
The lagging strand elongates away from the fork in short fragments called Okazaki fragments.
RNA primers are laid down on both strands before DNA polymerase can elongate.