Unit 4 - DNA Replication, The Cell Cycle, Mitosis, Cell Cycle Regulation, and Meiosis

replication fork

a y-shaped region where new DNA strands are elongating

helicase

enzyme that untwists the double helix at the replication fork. breaks the hydrogen bonding between nitrogenous bases

single-strand binding proteins

proteins that bind to and stabilize single-stranded DNA. prevents hydrogen bonds from forming back.

topoisomerase

enzyme that relieves the strain of twisting of the double helix by breaking, swiveling, and rejoining DNA strands. helps unwind DNA

primase

enzyme that synthesizes a RNA primer (5-10 RNA nucleotides) and the DNA strand starts from the 3’ end of RNA primer

DNA polymerase

enzyme that catalyzes the synthesis of new DNA at a replication fork

DNA polymerase I

enzyme that replaces RNA primers with DNA nucleotides during DNA replication

DNA polymerase III

enzyme that adds new nucleotides to the growing (leading) strand of DNA. can proofread as it’s adding nucleotides

leading strand

a daughter strand that has its 3’ end pointed toward the replication fork, so as the parental double helix unwinds, this daughter strand can be synthesized as one long, continuous polymer

lagging strand

a daughter strand that has its 5’ end pointed toward the replication fork, so as the parental double helix unwinds, a new DNA piece is initiated at intervals, and each new piece is elongated at its 3’ end until it reaches the piece in front of it. has okazaki fragments

DNA ligase

enzyme that joins two DNA fragments by forming a phosphodiester bond between them. makes this bond between the 3’-OH group and the 5’-Pi group of another fragment. (molecular glue!!!!)

telomeres

short, repeated non-encoding sequences “caps” at the end of chromosomes that prevent loss of genetic information as the result of this shortening

telomerase

enzyme that adds telomeres to the 3’ end of a DNA strand to prevent loss of genetic information

nuclease

enzyme that breaks the phosphodiester bonds that links nucleotides together to form nucleic acids.

cohesin

protein complex that holds sister chromatids together at the centromere after replication.

centrosome

organelle near the nucleus of a cell that contains centrioles. the main microtubule organizing center

centriole

an organelle that helps form spindle fibers that separate the chromosomes during cell division.

aster

radial array of short microtubules

kinetochore

a complex of proteins associated with the centromere of a chromosome during cell division, to which the microtubules of the spindle attach

separase

enzyme that triggers anaphase by cleaving the cohesin complex that holds sister chromatids together

kinetochore microtubule

attaches to centromeres via the kinetochore. helps to move and separate chromatids during cell division

non-kinetochore microtubule

elongates the cell in anaphase to allow the cell to divide