DNA Polymerase

DNA Polymerase

Enzyme that assembles nucleotides into a new DNA strand

DNA Polymerase I

DNA repair and some replication. Highest concentration

DNA Polymerase II

DNA repair. Middle concentration

DNA Polymerase

Have 3'-5' exonuclease; proofreading ability - keeps mutation rate below a certain level. Can only polymerize in a 5'-3' direction. Can only add nucleotides to an existing strand; can't start a new DNA strand

DNA Polymerase III

Holoenzyme, dimer of the core polymerase. Adds DNA nucleotides on to the end of the 3' primer. Majority of DNA replication. Lowest concentration

Replisome

DNA Polymerase III holoenzyme + other enzymes and accessory molecules.

Helicase

Circular enzyme that uses ATP to pry open DNA strands

Primase

Replicates/synthesizes the start of a new strand, the primer. Uses RNA in a 3'-5' way

DNA Polymerase I

Removes primer and lays new DNA.

Ligase

Supplies final phosphodiester bond that seals the new strands together.

Telomerase

Enzyme used in embryonic cells to maintain chromosome length. Uses its own RNA as a template.

RNA polymerase

Polymerizes from a ssDNA template in the 5'-3' direction. No primer needed and no exonuclease activity.

RNA-coding region

Starts from the 1st nucleotide that RNA will be complementary to and goes all the way down

Terminator

Beyond RNA-coding region where RNA polymerase falls off.

RNA polymerase I

Produces rRNA in the nucleolus

RNA polymerase II

Produces nRNA and snRNA in the nucleoplasm

RNA polymerase III

Produces 5S rRNA and tRNA in the nucleoplasm

Polyadenylation polymerase

Adds 50-250 A's when mRNA is processed; 3' poly-A tail

Splicing

Excising introns from pre-mRNA and rejoining exons.

Spliceosome

Made up of snRNA, which bind to small nuclear proteins to make the sNRPs

Homopolymers

RNA of only 1 repeating nucleotide

Unambiguous

Each codon designates only ONE amino acid

Redundant

One amino acid is often specified by more than 1 codon.

Wobble hypothesis

Relaxed base pairing at 3rd codon position - can withstand a little mismatch