AP Bio Cell Cycle

• Genome: all of the DNA in a cell
• Each species has a characteristic number of chromosomes
• Humans have 46 chromosomes or 23 pairs of chromosomes
• Somatic cells are all body cells except sperm and egg
• Gametes are sperm and egg, contain half the number of chromosomes, humans 23 chromosomes
• Each duplicated chromosome is made up of 2 sister chromatids attached by a centromere
• Sister chromatids have identical DNA sequences
• Once sister chromatids separate, they are considered individual chromosomes
• The mitotic phase alternates with interphase in the cell cycle
• Interphase is 90% of cell cycle
• G1 phase: cell grows
• S phase: DNA replication occurs, chromosomes are duplicated
• G2 phase: cell grows
• During all of the above the cell continues to function normally
• The features of mitosis that result in the production of genetically identical daughter cells include replication, alignment of chromosomes and separation of chromosomes.
• There are 5 phases of mitosis: Prophase, Prometaphase, Metaphase, Anaphase, Telophase.
• Prophase: chromatin condenses, nucleoli disappear, spindle begins to form
• Prometaphase: nuclear envelope fragments, chromosomes become visible each made of 2 sister chromatids.
• Metaphase: chromosomes line up on metaphase plate, centrioles at opposite poles
• Anaphase: sister chromatids separate, cell elongates
• Telophase: nuclear envelope reforms, chromosomes unwind to chromatin.
• Cytokinesis begins: cytoplasm of cell is divided
• Animal cells: cleavage furrow forms
• Plant cells: cell plate forms
• Prokaryotes divide by binary fission not mitosis
• The role of cyclins and cyclin-dependent kinases in the regulation of the cell cycle.
• There are a series of checkpoints to tell the cell either to continue dividing or to stop
• The major cell cycle checkpoints are: G1 phase checkpoint, G2 phase checkpoint and M phase checkpoint.
• The G1 phase checkpoint is the most important
• If the cell gets to ahead signal at this checkpoint, it usually divides
• If not pass G1 phase checkpoint cell remain in G0
• Some cells can be called out of G0 and move through G1 phase checkpoint.
• Kinases are proteins enzymes that control the cell cycle.
• Always in the cell, only active when connected to cyclin proteins.
• Therefore called cyclin-dependent kinases (Cdks).
• When cyclin combines with kinase it is called MPF.
• If enough MPF (Mitosis Promoting Factor) then cell will pass G2 checkpoint.
• During anaphase MPF switches itself off by destroying cyclin molecules, brining mitosis to a close.