AP Bio- topics 1 &2

what is the backbone of DNA composed of?

A phosphate backbone is the portion of the DNA double helix that provides structural support to the molecule

Compare eukaryotic and prokaryotic cells.

Prokaryotic cells are found in bacteria. Eukaryotic cells are found in plants and animals. Eukaryotic cells have a nucleus. Prokaryotic cells do not. Prokaryotic cells have a nucleoid. Eukaryotic cells do not.

describe step-by-step how DNA is replicated

Replication occurs in three major steps: the opening of the double helix and separation of the DNA strands, the priming of the template strand, and the assembly of the new DNA segment

in which stage of the cell cycle does DNA replicate?

S-Phase

descirbe Meselson and Stahl experiment that supported the semi- conservative model of DNA replication

The experiment done by Meselson and Stahl demonstrated that DNA replicated semi-conservatively, meaning that each strand in a DNA molecule serves as a template for synthesis of a new, complementary strand.

Differentiate between Purines and Pyrimidines

The purines (adenine and guanine) have a two-ringed structure consisting of a nine-membered molecule with four nitrogen atoms, as you can see in the two figures below. The pyrimidines (cytosine, uracil, and thymine) only have one single ring, which has just six members and two nitrogen atoms

True or False: Plasmids replicate seperately from chromosomal DNA

True

what functional group defines 3' end?

free hydroxyl group

what functional group defines 5' end of DNA?

free phosphate group

if an error occurs in DNA replication, how is it fixed?

promptly corrected by DNA polymerase by proofreading the base that has been just added. In proofreading, the DNA pol reads the newly added base before adding the next one, so a correction can be made.

what does it mean that DNA strands are anti parallel?

they run on opposite primes, from 3' to 5' and 5' to 3'