Mitosis and Mutation

• the three sources of mutation are: errors in DNA replication, DNA damage from radiation/chemicals, mistakes during mitosis/meiosis
• the four types of mutation are: silent, nonsense, frameshift, missense
• a missense mutation is a single base change that changes an amino acid and therefore the resulting protein
• a nonsense mutation is a single base change that codes for an early stop codon, causing only a fraction of the protein to be made
• a silent mutation is a single base change that results in no change in the resulting protein
• a frameshift mutation is a single base change that changes the reading from, and therefore most of the protein past the mutation is altered
• UV rays can cause DNA damage when rays hit a segment of DNA with many adjacent thymines, causing the formation of a bulky thymine dimer
• double stranded breaks damage DNA because they can cause rearrangements of whole chromosome segments
• errors in mitosis/meiosis can cause changes in DNA or an incorrect number of chromosomes in a cell
• mutations are random with respect to location, nature, and effect on fitness
• the g1 phase of interphase is the growth phase of the cell cycle and other cellular elements (except for DNA) are replicated. the cell also checks for sufficient nutrients
• the S phase of interphase is the phase of DNA replication
• the G2 phase of interphase is when the cell prepares for mitosis by growing to a sufficient size and checking DNA errors
• the G0 phase of the cell cycle is the resting phase and occurs when the environmental conditions are not sufficient for cellular division
• prophase is when chromosomes condense and the mitotic spindle is formed
• prometaphase is when the nuclear envelope breaks down and the spindle MTs attach to the chromosome by the kinetochore
• metaphase is when the chromosomes line up on the metaphase plate and the spindle MTs attach to the spindle poles
• anaphase is when chromosomes split and the MTs get shorter and the spindle poles move further apart
• telophase is when the nuclear envelope is reformed and the two sets of chromosomes go to opposite ends of the cell. the contractile ring is also formed
• mitotic spindles are a bipolar array of microtubules that pull apart the sister chromatids in anaphase and their formation is triggered by M-Cdk
• interpolar microtubules overlap antiparallel in the midzone of the cell
• kinetochore microtubules attach to the kinetochore at the centromere of chromsomes
• astral microtubules radiate outward form poles and help position the spindle in the cell
• positive ends of MTs radiate out from the poles while the negative ends of MTs are focused at the two spindle poles