DNA, RNA, Proteins

Nucleic Acids: “Information Molecules”

• DNA– Sugar

• Deoxyribose– Nitrogenous Bases

• Adenine• Guanine• Cytosine• Thymine

• RNA– Sugar

• Ribose– Nitrogenous Bases

• Adenine• Guanine• Cytosine• Uracil

Purines: 2 Rings

Pyrimidines: 1 Ring

Chargaff’s RulesT – A- 2 Hydrogen Bonds

C – G- 3 Hydrogen Bonds

DNA DNA Replication

DNA Replication

https://www.youtube.com/watch?v=27TxKoFU2Nw

Origin of Replication

• Site where replication begins• Where nucleotide add = Replication Fork

• Prokaryotes have a single starting spot• Eukaryotes: have multiple starting spots

DNA Polymerase

• Creates DNA molecules by assembling nucleotides

• It is an enzyme

• DNA Polymerase I: removes RNA primers and replaces them with DNA bases by adding to the 3’ end of the previous fragment

• DNA Polymerase III: adds nucleotides in the 5’3’ direction

Leading Strand

• Runs 3’ 5’• Copies towards the replication fork• Primase adds RNA primer to start chain– One primase for the entire strand

Lagging Strand

• Runs 5’ 3’• Copies away from the replication fork• Primase: adds RNA primers at various spots as

fork opens• Short segments = Okasaki fragments

RNA Primase?

• This is an enzyme that attaches to DNA in order for other enzymes to come and replicate DNA

• Once the chain replicates, the RNA primase that has bonded to the DNA strand is removed by an exonuclease

• DNA Polymerase I: replicates the DNA area where the RNA Primase once was located

IMPORTANT

• The very last section when the primer is removed from the lagging strand

• The DNA that replicated is now shorter• Therefore, the code shortens with each

replication