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18 terms

Williams Bio Quiz #2 Terms

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DNA polymerase I
replaces RNA (primers) with DNA; has both polymerase and exonuclease (degrading of nucleotides) activity
DNA polymerase III
catalyzes elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain; does the majority of synthesis
ligase
takes gaps/nicks in DNA (small holes with 5' and 3' ends) and fills them in (related to Okazaki fragments)
primase
joins RNA nucleotides to make the primer using the parental DNA strand as a template
helicase
unwinds the two DNA strands for replication
single strand binding proteins
bind to the unwound & unpaired DNA strands, keeping them from re-pairing
DNA gyrase
works ahead of the replication fork; cuts DNA to relieve tension as unwinding is happening, and seals it back together
telomere
tandemly repetitive DNA at the end of eukaryotic DNA; protects coding region of the organism's DNA from being eroded during successive rounds of replication
telomerase
an enzyme in eukaryotic cells that can add telomeres to the ends of chromosomes after they divide
mRNA
messenger RNA: carries a copy of the protein-coding gene sequence (from DNA) to a ribosome
rRNA
catalyzes peptize formation and provides the structural framework for ribosomes
tRNA
carries amino acids to ribosomes for assembly into peptides
things necessary for transcription
1) DNA template; 2) ribonucleoside triphosphates (ATP, CTP, etc.); 3) RNA polymerase to catalyze reaction (1 in bacteria, 3 in eukaryotes)
RNA polymerase
enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template
initiation
(transcription) involves promoters, or short sequences to bind/orient RNA polymerase
elongation
(transcription) unwinding of DNA, reading of template strand 3'->5' and transcription 5'->3'
termination
(transcription) ending of transcription signaled by specific base sequence; RNA polymerase falls or is pulled away
codon
a specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid