12.3 DNA Replication

Key Terms:

Replication: This process occurs late in the interphase of the cell cycle, it ensures that each cell has the same complete set of DNA molecules.

DNA polymerase: It is an enzyme that joins individual nucleotides to produce a new strand of DNA.

Telomeres: DNA at the tips of chromosomes.

Histones: Proteins around which chromatin are tightly coiled.

Notes

Replication is when the DNA separates into two strands forming replication forks and then following base pairing they get complementary strands. (Such as A-T or C-G)

Enzymes: Replication is done by many enzymes the first separating the DNA molecule by breaking the hydrogen bonds between base pairs. When they separate each strand gives an outline for what complementary base it needs (A-T, C-G). The enzymes are named for their function since they are specific. The primary enzyme is DNA polymerase (see Key Terms). Another function enzymes perform is making sure that each new DNA strand is a copy of the original.

Telomeres: Telomerase replicates it, because it is difficult to replicate. Since it rapidly divides it helps genes not be damaged.

Prokaryotic DNA replication: Occurs during the S phase of the cell cycle. DNA is found in a single, circular, DNA molecule in the cytoplasm. Replication doesn't start until the regulatory proteins bind to a single spot on the chromatin. KEY: Replication in most prokaryotic cells starts from a single point and proceeds in two directions until the entire chromosome is copied.

Eukaryotic DNA Replication: Occurs during the S phase of the cell cycle. Their DNA is in the nucleus packaged into chromosomes. Eukaryotic chromosomes are bigger than prokaryotic cells. Key: In eukaryotic cells, replication may begin at dozens or even hundreds of places on the DNA molecule, proceeding in both directions until each chromosome is completely copied. Proteins check for damage or mismatched base pairs before the DNA is replicated, but sometimes they are replicated and base sequences may be changed and cause bad side effects. The two new DNA copies are separated at anaphase.