BIO 201 Lecture 28: Lecture 28 - Spindle assembly checkpoint; cytokinesis
6 Sep 2018
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If anything goes wrong during this step, it can be very (cid:271)ad for (cid:272)ells Abnormal segregation of chromosomes leads to chromosomal nondisjunction. Karyotype: the number and types of chromosomes in a cell. Aneuploidy: abnormal number and/or type of chromosome(s); usually incompatible with life. Nondisjunction: abnormal chromosome segregation during mitosis or meiosis. The kinetochore: the protein complex at centromere that holds sister chromatids together. Cohesion protein in the kinetochore holds sister chromatids together until anaphase. Cohesion is degraded by proteases as soon as the spindle is complete and chromosomes are aligned. At metaphase, microtubules pulling from opposite directions might impart tension on the kinetochores. Hypothesis: tension on the kinetochore causes cohesion degradation. Experiment: use a glass needle to pull on a chromosome before 2nd mt attaches. Tension is the signal at the metaphase-to-anaphase transition. Aneuploidy: can result from errors of g1/s or spindle assembly checkpoints. Abnormal hybrid chromosomes can result from dna repair problems at either g2/m or g1/s.
