Biology Unit 2

IB

Helicase

An enzyme which unzips and separates the two DNA strands to allow for replication by breaking hydrogen bonds between base pairs.

DNA polymerase III

Enzyme that starts replication by the RNA primers, and in a 5’ to 3’ direction, adds deoxynucleoside triphosphates, cleaving their two excess phosphate groups, using that energy to link the nucleotide to the strand.

Deoxynucleotide triphosphate(dNTP)

Free DNA nucleotides with three phosphate groups, used for DNA replication.

Semi-conservative

After a new DNA strand is replicated, one strand is copied and one is the original strand.

Meselson & Stahl

Discovered replication was semi-conservative

RNA primase

Adds RNA primers to signal DNA polymerase III where to start replication (one on the leading, multiple on lagging)

Okazaki fragments

The lagging strand is synthesized in sections called…

DNA polymerase I

Removes the RNA primers and adds DNA nucleotides.

DNA ligase

Joins the Okazaki fragments together to one continuous strand.

DNA Gyrase (Topoisomerase)

Helps with separating the DNA by relieving strain.

Single strand binding proteins (SSB)

Helps keep the strands apart during replication by keeping the nucleotides from reforming hydrogen bonds.

RNA polymerase

Opens the helix and adds RNA nucleotides matching the template strand, creating an mRNA.

mRNA

A copy of one DNA strand, used to form a polypeptide.

Codon (triplet)

A set of three nucleotides which codes for 1 of 20 amino acids.

tRNA

Has an anticodon and a corresponding amino acid.

Ribosome

Made up rRNA, with a small and a large subunit. Has three binding sites for tRNA; A, P and E.

Initiation

Process where the small ribosomal unit binds to the mRNA, moving along it until it reaches the start codon where the tRNA with the matching anticodon binds to it, with finally the large subunit binding to the structures.

Elongation

A process where the ribosome moves along the mRNA, with tRNA entering the binding sites and adding amino acids to the polypeptide chain with a peptide bond. The chain is always moved to the new tRNA that recently enters.

Termination

When the ribosome reads a stop codon, translation stops, the polypeptide chain is released and the translation complex is disassembled.

Translocation

A process carried out simultaneously with elongation, tRNAs are moved from one site to another during elongation, from A, to P, to E.