Scott_Handout4-key - 2/22/2010 MCB 104; Handout #4 1. What...

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2/22/2010 MCB 104; Handout #4 1. What are kinetochores, and where are they found? Other key terms to know: centromere, cohesin, Dam1. Stanfurd students often confuse centromeres with centrosomes. Don’t make the same mistake. Kinetochores are protein complexes that bind to the centromere. The centromere is a piece of DNA near the middle of a chromosome. Dam1 is a ring-shaped protein that is associated with the kinetochore and allows chromosomes to slide along a microtubule (MT). Cohesin holds sister chromatids together prior to anaphase. 2. Which of the following pairs are genetically identical, and which are not? homologous chromosomes at the end of mitosis [ not identical; barring a DNA replication or mitotic division error, homologous chromosomes are not genetically identical] ; sister chromatids at the end of mitosis[ genetically identical] ; homologous chromosomes at the end of meiosis [ not identical] ; sister chromatids at the end of meiosis [ not identical due to crossing over] . 3. In mitosis, cohesin is released just before anaphase begins. In meiosis, cohesin is released along the chromosome arms prior to anaphase I, and is released near the centromere in during anaphase II. Why would you want to release cohesins all at once during mitosis, but sequentially during meiosis? Releasing cohesion on just the arms during meiotic prophase and metaphase allows frees- up individual chromosome arms so they can cross-over with their homologs . Releasing cohesins all at once in mitotic anaphase allows the sister chromatids to separate; there’s no crossing-over. 4. Is the centrosome necessary for spindle formation (note: Berkeley’s own Rebecca Heald did an experiment in frog egg extracts that answered this question—be familiar with the experimental approach)? Key components of the spindle to know: astral microtubules, kinetochore microtubules, polar microtubules. Which MTs anchor the
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This note was uploaded on 04/05/2010 for the course MCB 104 taught by Professor Urnov during the Spring '09 term at University of California, Berkeley.

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Scott_Handout4-key - 2/22/2010 MCB 104; Handout #4 1. What...

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