BIO 151 1st Edition Lecture 19 Outline of Last Lecture 1. Coat proteins2. Prokaryotic cell division3. Eukaryotic chromosomes4. Mitosis5. Mitotic spindle arranges and moves chromosomes6. How does the mitotic spindle work?7. Cytokinesis8. Cytokinesis different if there is a cell wall9. The cell cycle10. Cell cycle checkpointsOutline of Current Lecture 1. Cell cycle checkpoints2. Cell cycle regulation3. Mitosis gets you genetically identical copies4. Lack of variability is evolutionary suicde5. Sexual reproduction meiosis6. What does a eukaryotic cell's chromosomes really look like?7. Important terminologyCurrent Lecture - 3/4/15Cell cycle checkpoints:- G1 - cell large enough, nutrients, signals?- G2 - DNA duplicated- M - chromosomes on signal- mitosis, or M-phase promoting factor = MPF- MPF drives cells through the G2 checkpoint- MPF = 2 proteins: cyclin - binds to and activates cyclin-dependent kinase (CDK), levels of cyclin change (CDK don't)- enzyme that acts as switchCell cycle regulation:- cyclin-fluctuating concentration during cell cycle- kinase (cyclin-dependent kinase, CDK), mostly constant during cell cycle- different cyclins and CDKs for every checkpoint- output of cell cycle is an identical copy of the cellMitosis gets you genetically identical copies:- success in biology is making copies of genetic blueprintLack of variability is evolutionary suicide:- what we need is "just enough" genetic variability- mutations - new variations- kind of rareThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- too many is disastrous- sexual reproduction - rearranging the existing variability into new combinationsSexual reproduction and meiosis:1. Variability is the raw material through which adaptations form.2. If you can't adapt, you disappear.3. Mitosis/cloning/asexual reproduction does not promote a high variability in genetic "resources"4. Mutations generate variation in protein and RNA functions and patterns of expression5. New combinations of mutations generate new functions that might be better adapted6. So we need to continually mix these together in new combinations to maintain the biggest pool of genetic variability7. This is a genetic investment in the future and occurs in most eukaryotes via sexual reproduction. - mitosis don't care about homologous chromosomes- sex/meiosis, they are really importantImportant terminology: - a pair of homologous chromosomes includes 1 chromosome from each parent, each with member of the pair carrying similar genetic info.- the 46 chromosomes in a human somatic (non-gamete) cell are in 2 sets of 23: one from the mother and one from the father (23 pairs of homologous chromosomes)- a diploid cell (2n) has 2 sets of chromosomes - most of you is diploid- for humans, the diploid number is 46 (2n=46)- for humans, the haploid number is 23 (n=23)- haploid cells (1n) has 1 set of chromosomes- in humans, haploid cells are the gametes (eggs and sperm)- sexual reproduction requires the union of them- but diploid and diploid would be 4-ploid...- somehow we must reduce the genetic material in the egg and sperm to 1/2 the diploid level (1n, haploid)- haploid and haploid = diploid (1n+1n=2n)- the spindle provides a mechanism for separating copies of the genetic material (compare mitosis)- a gamete (sperm or egg) contains a single set of chromosomes, and is haploid (n)- for humans, the haploid number is 23 (n=23)- each set of 23 consists of 22 autosomes and a single sex chromosome- in an unfertilized egg (ovum), the single sex chromosome = x- in a sperm cell, the sex chromosome may be either X or
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