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What does Helicase do?
Unwinds parental double helix at replication forks
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what does a single-strand binding protein do?
Binds to and stablizes single-stranded DNA until it can be used as a template.
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Topoisomerase
relieves "overwinding" strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands.
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Primase
Synthesizes an RNA primer at 5 prime end of leading strand and of each Okazaki fragment of lagging strand.
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DNA pol III
Using parental DNA as a template, synthesizes new DNA strand by covalently adding nucleotides to the 3 prime end of a pre-existing DNA strand or RNA primer
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DNA pol I
Removes RNA nucleotides of primer from 5 prime end and replaces them with DNA nucleotides
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telomerase
an enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells, thus restoring their original length and compensating for the shortening that occurs during DNA replication.
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DNA ligase
joins 3 prime end of DNA that replaces primer to rest of leading strand and joins Okazaki fragments of lagging strand
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primary transcript
the initial RNA transcript, including those coding for RNA that is not translated into a protein. Consists of pre-mRNA, to later be modified
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genetic code
only 4 nucleotide bases to specify 20 amino acids, how many bases correspond to an amino acid?
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flow in bacterial cell
mRNA produced by transcription is immediately translated without additional processing
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flow in eukaryotic cell
nucleus provides a separate compartment for transciption, so pre-mRNA is processed before leaving nucleus as RNA
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codons
triplets of nucleotide bases, smallest units of uniform length that can code for all the amino acids (4^3=64). Each specifies an amino acid to add to the growing polypeptide chain
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triplet code
flow of information from gene to protein, genetic instructions for a populpeptide chain written in the DNA as a series of nonoverlapping 3-nucleotide words
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for each gene, only one of the two DNA strands is transcribed. It provides the seqence for an RNA transcript.
template strand
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