The Cell Cycle I prefer Monkeys At The Circus Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Interphase represents about 90% of the cell cycle Cells perform their specific tasks while in interphase Cells must have access to their DNA so the DNA needs to be in chromatin form (spread out) G1 phase (Growth phase) ● Cell recovers from cell division ● Cell becomes larger ● Organelles must be replicated Cells are most functional directly after G1 phase G1 checkpoint checks for: 1.Cell Adhesion Is the cell attached to the extracellular matrix? Are we around the cells we’re supposed to be around 2.Cell Density Is there enough room for the cell to divide 3. DNA Damage If a cell fails the G1 checkpoint it is either destroyed or goes to the G0 phase where the cell cycle is paused until the errors are corrected The G0 phase is also entered if the body sends a signal to stop producing cells Cancer Cells usually do not go through the G1 checkpoint S phase synthesis phase ● DNA is copied ● Producing DNA is called DNA synthesis G2 phase growth phase ● Cells grows in order to get ready to divide ● Cell becomes slightly larger ● Extra copies of important organelles (eg mitochondria) are produced It is very important that the cell leaves G2 phase because if not it will produce double the substances it should produce G2 checkpoint ● Checks for errors in DNA replication If cell doesn’t pass the errors are either fixed or the cell is destroyed M Phase Mitosis ● A single parent cells produces two genetically identical daughter cells ● Produces Somatic Cells (normal cells) ● ● ● Meiosis A single parent cell produces four genetically unique cells with half as many chromosomes Go from diploid to haploid Produces Gametes in Animals (sperm and egg) Cytokines Actual division of the cell that occurs in telophase Telophase ends when cytokines completes DNA organization Law Of Independent Assortment In Prophase I, when tetrads form, the orientation of one tetrad has no effect on the orientation of the rest of the tetrads Law Of Crossing Over Nondisjunction Failure of chromosomes to separate during anaphase I or Anaphase II of meiosis Nondisjunction in single chromosomes Trisomy Non disjunction for all chromosomes Polyploidy Polyploidy Results in extra sets of homologous chromosomes (4n 8n 12n) Aneuploidy An abnormal number of chromosomes of that type Monosomy Only one chromosome of that type Trisomy Three chromosomes of that type Down syndrome Trisomy of the chromosome 21 Sex chromosomes trisomy are far less lethal than normal cell trisomy Deletion Part of the chromosome is removed ● ● This doesn’t cause problems if the persons other chromosomes have the deleted part because usually the other chromosome can produce enough for both Inbreeding is a problem because the other person is more likely to have the deleted part of the chromosome as well Duplication Multiple copies of the same gene on a single chromosome Overproduction occurs Translocation One portion of a chromosome is moved to a non homologous chromosome Immediate result ● Some cells will produce things they shouldn’t produce ● Some cells will not produce what they should produce Long term Results ● Offspring will have either an overproduction or underproduction of certain genes Fusion Two non homologous chromosomes join together ● Length of the chromosome changes ● Shape of the chromosome changes ● 2 centromeres with 3 telomeres Inversions Genes switch places on a chromosome ● non immediate effects ● During crossing over both deleting and duplication will happen
