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17 Cards in this Set

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Helicase
During replication, it unwinds the DNA helix, forming a Y shaped replication fork.
SSBP
Single stranded binding proteins attach to each strand of the uncoiled DNA to keep them separate. Used during replication
Topoisomerase
Found in replication, break and rejoin the double helix, allowing the twists to unravel and preventing the formation of knots.
Leading strand
The strand of DNA that is replicated in from the 3' --> 5' template strand. The strand is produced continuously in the 5' --> 3' direction.
Lagging strand
The strand of DNA that is replicated in the 5'--> 3' direction, must be replicated in short segments known as okazaki fragments that are connected by DNA Ligase.
Primase
Begins replication by producing a short segment of RNA (primer). The leading strand and every okazaki fragment must have an RNA primer.When the primer is in place, DNA pol can attach the nucleotides to the primer.
Telomerase
Attaches to the end of a template strand and extends it by adding a short DNA sequence over and over again. This allows elongation of the lagging strand to continue.
mRNA
Single strand of RNA that provides a template used for sequencing amino acids into polypeptides. Contains the triplet codon that codes for a single amino acid.
tRNA
A short RNA molecule that is used for transporting amino acids into their proper place on the mRNA template. The 3' end attaches to an amino acid. Another portion of the tRNA is the anticodon (the part that base pairs with the codon from mRNA). About 45 different tRNA's base pair with the 61 codons that code for amino acids.
rRNA
The building blocks of ribosomes. The nucleolus is an assemblage of DNA actively being transcribed into rRNA. Ribosomes have three binding sites.
Transcription
Initiation- RNA pol attaches to the promoter region on the DNA and begins to unzip it into two strands.
Elongation- Occurs as RNA pol unzips the DNA and assembles RNA nucleotides using one strand as a template. Occurs in the 5' --> 3' direction
Termination- occurs when the RNA polymerase reaches a special sequence of nucleotides that serve as a termination point.
mRNA processing
Before an mRNA molecule can leave the nucleus, it must be altered. A 5' cap can be added, a poly-A tail, RNA splicing (to remove introns) and alternative splicing (allows different mRNAs to be generated from the same RNA transcript)
Translation
the mRNA, tRNA and ribosomal subunits are transferred across the nuclear envelope and into the cytoplasm. Here the amino acids attach to the 3' end of the tRNA.

Initiation- begins when the small subunit binds to a special region and fMet binds. Also large subunit joins.
Elongation- begins when the next tRNA with amino acid binds to the A site. Translocation occurs.
Termination- occurs when the ribosome encounters a stop codon.
Silent mutation
When the new codon codes for the same amino acid.
Missense mutation
Occurs when the new codon codes for a new amino acid.
Nonsense mutation
Occurs when a new codon codes for a stop codon.
Ways to repair replication errors
Proofreading (DNA polymerase checks that the new nucleotides are correct), mismatch repair (enzymes repair errors after DNA pol has checked), excision repair (enzymes remove nucleotides caused by mutations).