- double helix (2 strands)

- contain base pairs C, T, A, G (hydrogen bonding)

- 5' & 3' carbon on sugar is where phosphates are connected creating a phospho-diester linkage

- is copied during S phage

- is semi-conservative where 1 strand is old and 1 is new

- an area where DNA separates into 2 strands and DNA synthesis occur

Significance of origin Recognition

Complex (ORC)

- ORC binds to origins of replication to begin replication

- Cdc6p- is a replication activator protein

- once ORC binds, proteins load the MCM (mini- chromosome maintainance) to form "licensed"

- ORC, Cdc6p & MCM must be phosphorylated for DNA replication to start

- CDC & DDK become active in late G1 activating the MCM helicase & load on the replisome that contains the DNA polymerase

-DDK phosphorylates MCM inhibiting licensing

separates the DNA helix

-unwinds the DNA

-Positive supercoils if >10.4

-Negative supercoil if < 10.4

- Prevents "overwinding" of DNA

-type 1 topoisomerase

- cuts only 1 strand of DNA

-inhibited by Camptothecin (treats cancer)

-type 2 topoisomerase

- cuts both DNA strands

-inhibited by etoposide (treats cancer)

Importance of single stranded

binding protein (SSB)

- prevent helix from reforming temporarily

- builds a RNA primer starting from the 5' end of the new DNA strand

- Consists of a RNA polymerase & a DNA polymerase

- polymerase ε & δ responsible for building a new strand 5' to 3' via covalent bonds

Polymerase ε is the leading strand (continuous)

- goes toward the fork

Polymerase δ is the lagging strand (discontinuous)

- goes away from the fork

- contains okazoki fragments

-repeats one nucleosome @ a time

-Lagging strand of telemeres cannot be replicated

seals the gaps of okazoki fragments on lagging strands

- a phosphodiester bond

- a specific enzyme with intergrated RNA template

- a RNA dependent -RNA polymerase

- telomere contain a sequence of tandom repeats of TTAGGG

-PCNA (proliferating cell nuclear antigen)

- a beta sliding clamp that keeps the DNA on the polymerase