BIOL 120 1st Edition Lecture 11 Outline of Last Lecture I Membrane Structure II Membrane Proteins III Cell division beginning Outline of Current Lecture I The Cell Cycle II Chromosomes III Mitosis events IV Checkpoints Current Lecture I The Cell Cycle A This is the orderly sequence of events that helps a eukaryotic cell through duplication of its chromosomes in order to undergo cell division 1 Steps i G1 preparing for replication ii S DNA is duplicated iii G2 preparing for nuclear division a interphase G1 S G2 iv M division of the nucleus 2 G1 and G2 are when the cell grows in order to have space to duplicate organelles in order for daughter cells to be functioning and normal size cells These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 3 Interphase i includes G1 S G2 ii G1 and G2 do not have DNA synthesis iii During this phase organelles replicate and additional cytoplasm is created iv S phase is the only phase where DNA duplication occurs synthesis phase II Chromosomes A Chromosomes contain a single long double helix of DNA wrapped around proteins these proteins help pack the chromosome so that it fits in the nucleus B Gene a section of DNA that encodes a specific protein or RNA the number of bases determines the function C Mitosis and Chromosomes i purpose of mitosis is to spread chromosomes between daughter cells replicated before mitosis ii when mitosis starts the chromosomes condense into compact structures that are easy to move around the cell at the end of mitosis the copied chromosomes are divided between two daughter cells D Replication i Chromatid the DNA copies in a replicated chromosome ii Centromere where chromatids are joined together during mitosis iii Sister chromatids chromatids from the same chromosome E Changes during the cell cycle i chromosomes go from relaxed during interphase G1 S G2 to condensing during mitosis III Mitosis Events A Mitosis is the division of replicated chromosomes in order to form two daughter nuclei with identical chromosomes and genes B Accompanied by cytokinesis C During this process the sister chromatid separate to form independent chromosomes one copy goes to each daughter cell D Subphases of Mitosis i Prophase a chromosomes condense b spindle apparatus assemble 2 centrioles move to opposite poles to form these c nuclear envelope breaks down to allow access to chromosomes ii Prometaphase a nuclear envelop disassembles b microtubules attach each sister chromatid connects to opposite poles c congession chromosomes move to center of cell iii Metaphase a chromosomes align along metaphase plate where the cell will eventual divide iv Anaphase a centromeres split sister chromatids are pulled apart and to opposite poles v Telophase a Whatever appears disappeared in prophase is put back or removed spindle apparatus disassembles nuclear envelop reforms nucleolus reappears vi Cytokinesis a this is when the cytoplasm divides to form two new daughter cells b cell types i plant cells vesicles come into the middle containing cell wall content and create a new cell wall to divide the cell in half they fuse to create a cell plate ii Animals fungi slime molds follow the cleavage furrow filaments contract in the cell membrane and cause it to pinch inward iii Bacteria do not undergo cytokinesis but go through fission to separate E Mitosis Promoting Factor MPF i present in the cytoplasm of M phase and is in charge of beginning mitosis ii Composed of a protein kinase enzyme catalyzes the transfer of a phosphate group from ATP to a target protein phosphorylation b cyclin functions as a regulatory protein iii concentration increases during interphases peaks in M phase and decreases at the end of mitosis IV Checkpoints A in charge or regulating the cell cycle to prevent mutations or deformities i at each checkpoint the cell decides if the division should continue or not ii if checkpoints fall can lead to the development of tumors B three distinct checkpoints G1 G2 M C G1 checkpoint i occurs late in G1 determines if the cell will continue to divide or not based on cell size nutrients available social signals from other cells and the health of the DNA ii P53 a tumor suppressor is used at this checkpoint D G2 checkpoint i stops cell growth if the chromosomes have not been replicated properly or if the DNA is damaged E M checkpoint i cell growth stops at his stage if chromosomes are not properly attached to the spindles preventing incorrect chromosome separation do not want daughter cells to have different number of chromosomes