Central Dogs massss

Helicase

Unwinds the DNA double helix during replication

DNA Polymerase III

Primary enzyme that adds nucleotides to growing DNA strand in prokaryotic replication

DNA Polymerase α

Starts DNA replication by adding DNA to RNA primer in eukaryotes

DNA Polymerase δ / ε

Extend the leading and lagging strands in eukaryotic DNA replication

Ligase

Seals the nicks between Okazaki fragments on the lagging strand

Primase

Lays down RNA primers so DNA polymerase can begin synthesis

Topoisomerase

Relieves supercoiling ahead of the replication fork

Prokaryotic transcription location

Cytoplasm

Eukaryotic transcription location

Nucleus

Prokaryotic RNA processing

No RNA processing; transcription and translation occur simultaneously

Eukaryotic RNA processing

Includes 5' cap, poly-A tail, and splicing of introns

RNA polymerase in prokaryotes

Single RNA polymerase for all RNA types

RNA polymerases in eukaryotes

Three types: RNA Pol I (rRNA), RNA Pol II (mRNA), RNA Pol III (tRNA)

Strand synthesis direction

New DNA and RNA strands are synthesized 5' to 3'

Template strand direction

The DNA template strand is read 3' to 5'

Okazaki fragments

Short DNA segments synthesized on the lagging strand during replication

Lagging strand

The strand synthesized discontinuously away from the replication fork

Leading strand

The strand synthesized continuously toward the replication fork

Promoter

Specific DNA sequence where RNA polymerase binds to initiate transcription

Codon

Three-nucleotide sequence on mRNA that codes for an amino acid

Ribosome A site

Accepts incoming aminoacyl-tRNA

Ribosome P site

Forms peptide bond between amino acids

Ribosome E site

Exit site for empty tRNA

Intron

Non-coding sequence removed during RNA splicing

Exon

Expressed sequence retained in mature mRNA