Bio 111 DNA Replication

DNA replication

chromosomes go from having a single chromatid to sister chromatids in S phase

nucleic acids

• information molecules

• DNA and RNA

• strings (polymer) of individual nucleotides (monomers) each containing a nitrogenous base, sugar, and phosphates

nucleic acid bases

A,C,G,T,U

DNA bases

AT, GC

RNA bases

AU, GC

pyrimidines

smaller bases; CUT

*Egyptians had to CUT a lot of stone to make PYRAMIDS

purines

bigger bases- 2 rings; AG

*PURE As Gold

purines and pyrimidines

bases; pair with each opposite

phosphates in nucleic acids

3 of them; energy in bonds is used to drive something forward

sugar in nucleotide

made up of 1 prime through 5 prime carbons

1’ base

2’ H (DNA) or OH (RNA)

3’ hydroxyl (OH)

4’

5’ where phosphates attach

what is DNA a polymer of

deoxyribonucleotides

phosphodiester bonds

bonds between 3’ hydroxyl group and 5’ phosphate groups; covalent

directionality

DNA is an antiparallel double helix held together through complementary base pairing

antiparallel

• parallel, just running in opposite directions

• double stranded DNA has one strand running 5’ to 3’ and the other is 3’ to 5’

complementary base pairing

• A with T, G with C

• purine with pyrimidine

• bonded by non-covalent hydrogen bonds

DNA replication

• incoming nucleotide is added to the 3’ end of the template

• the phosphates attach to the hydroxyl group on the 3’ carbon of the template DNA

• reaction occurs in 5’ to 3’ direction

daughter DNA

• new strand of DNA being made

• 5’ to 3’

template DNA

• existing strand so you know what nucleotide to add

• 3’ to 5’

replication fork

created by helicase separating the strands of the template DNA

leading strand

made from replication fork

1) continuously made

2) towards fork, right to left

3) goes in 5’ to 3’ direction, adding to 3’

lagging strand

made from replication fork

1) discontinuously made

2) away from fork, left to right

3) 5’ to 3’

RNA primase

• makes RNA primer

• made in 5’ to 3’ direction

• complementary

RNA primer

first nucleotide

DNA polymerase

• synthesize/make/polymerize DNA

• 5’ to 3’

• complementary

• chopping RNA 1 by 1 while simultaneously addding nucleotides (removing RNA primer)

ligase

stitch Okazaki fragments with phosphodiester bonds to make energy

ligand

binds Okazaki fragments 

helicase

• enzyme that makes fork/does unzipping by breaking hydrogen bonds using ATP

• moves left to right

• creates single stranded DNA

• as DNA unwinds it starts to supercoil and tangle (in a bad way)

leading strand

• moves towards the fork

• 5’ to 3’

topoisomerase

• relaxes DNA

• untwisting it ahead of the fork

• relieving stress (tangled supercoil) induced by helicase

single strand binding proteins

• binds single strand of DNA and stabilizes it

• allows RNA primase, DNA polymerase and ligase to come in and do their jobs

DNA replication proteins

1) primase

2) DNA polymerase

3) ligase

4) helicase

5) topoisomerase

6) SSBs