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http://kmarsh2.umwblogs.org/2008/10/24/cartoon-mitosis/ Nice animation, includes recombination http://www.johnkyrk.com/meiosis.html Mitosis and Cell Division Mitosis and Cell Division Goals: • Scaling: Nucleotide, Gene, Chromosome--and how many of each • Differences between mitosis and meiosis • Predict and describe meiotic results • Master concepts referred to by: allele, dominant, recessive, linkage Mitosis and Cell Division • You run a cake-making company • Order comes in for a cake • What information do you need? – It’s ‘old-fashioned’- no photos Scaling • A gene is ~1,000-100,000 basepairs* • A chromosome is tens or hundreds of thousands of genes • A genome is 1-100s of chromosomes • A genotype refers to the alleles present in a given genome • Human genome is ~3,000,000,000 basepairs • Human genome is (currently guesstimated at) ~20-30,000 genes** • Human genome is ~1 meter of DNA Mitosis and Cell Division Mitosis and Cell Division • Gene: Segment of DNA that represents all information for a product as well as when and where to make the product • Allele: A version (or flavor) of a gene; two alleles of the same gene my differ by a nucleotide or dozens of them--generally a small number • Dominant/recessive: Two alleles enter; one allele leaves (which version manifests in the organism) NOT which version is more common! • Mitosis vs Cell Division • More in the lab manual & Vocab exercises! Windows on the gene: eyes • Find a brown- and a blue-eyed person. Look deep into their eyes & try to figure out the difference • What does it mean genetically when we say ‘brown eyes are dominant’? – One gene, two alleles • Why should that be so? What do brown alleles got that blue do not? ‘Ripped’ from Headlines • Blue eyes arise from a DNA change that prevents creation of melanin in the eye specifically • Mutation appears identical in all blue-eyed folks Meaning? • Headline: Blue eyes result of ancient genetic ‘mutation’ – It’s not a ‘mutation’; it’s a mutation A Couple Things to Think About… Mitosis and Cell Division • How many cells – When you were “0”? – Now? • What do cells DO? https://eapbiofield.wikispaces.com/file/view/12_05CellCycle-L.jpg What happens in each “Stage?” What if a cell isn’t “listening”? • Malignant Tumor – grows aggressively, invades surrounding tissue, metastasizes • Benign Tumor – lacks malignant tumor’s properties • Benign tumors CAN cause “mass effects” What if a cell isn’t “listening”? • Carcinoma - external/ internal coverings of body • Sarcoma - support tissues (bone, muscle) • Leukemia, lymphoma - bloodforming tissue cancers And now, back to our program It’s all in a name • • • • • • • • • Chromosome Gene Chromatid Allele Homologous Dominant Recessive Spindle Fiber Centromere 1 “Chromatid” can also be a chromosome; it has all the genes on it. 1 “Chromatid” can also be a chromosome; it has all the genes on it. 1 “Chromatid” can also be a chromosome; it has all the genes on it. This 1 “Chromatid” can also be a chromosome; it has all the genes on it. This Is just a copy of this So, in this scenario… From Mother Chromosome 1 Chrm 2 From Mother Chromosome 1 Chrm 2 From Father Chromosome 1 Chrm 2 This is a DIPLOID Nucleus/Cell Chromosome 1 (from mother) Chromosome 1 (from father) Chromosome 1 (from mother) Chromosome 1 (from father) Copied during Interphase Copied during Interphase Chromosome 1 (from mother) Copied during Interphase Chromosome 1 (from father) Copied during Interphase So after replication… So after replication… Chromosome 1 (from mother) Chromosome 1 (from father) Chrm 2 Chrm 2 Condensed versions during mitosis/meiosis This is ALSO a diploid nucleus/cell This is a DIPLOID Nucleus/Cell Mitosis and Cell Division Why are chromosomes usually shown like this? Back to program Pay attention to the ‘nubbins’ Mitosis and Cell Division • What do our bead models represent? Mitosis and Cell Division • SHOW ME • You can do a lot of fuzzy math (and fuzzy biology and fuzzy chemistry and fuzzy...) up there • Drawing/speaking/writing forces precision; reveals missing links Mitosis and Cell Division • Pick two traits • Pick a dominant & recessive outcome arising from different alleles • You all start off heterozygous Mitosis and Cell Division • Point at some of your cells that ‘do’ mitosis? • What’s the goal/purpose of this thing called ‘mitosis’? • So what must the first step be? Do it. Mitosis and Cell Division • Let’s do it • What are ‘homologous’ chromosomes? • How does ‘cell’ know they go together? Mitosis and Cell Division • Point at some of your cells that ‘do’ mitosis? • What’s the goal/purpose of this thing called ‘mitosis’? • So what must the first step be? Do it. • Now what must be achieved? – Any half? If not, how pick the appropriate half? • How do your final results compare with starting? Mitosis and Cell Division • What comes after MITOSIS? Meiosis • Why have sex? • What do you want the cells to look like at the end of meiosis? • How much are you ‘like’ your mom and dad? • Do ‘mother’ chromosomes have to stay together? Meiosis • Let’s do it • How diverse are your ‘gametes’? • Is that enough? Meiosis • Recombination • ‘Homologous’ chromosomes can exchange genes Meiosis Where should the circled site on Chromo1 recombine with Chromo2? 1 2 3 Meiosis • Pick two ‘traits’ • What is dominant/recessive? Meiosis • First, make a copy--b/c that’s the way it happens • Pair the pairs: duplicated mom’s & dad’s contributions pair • Recombine (randomly) Meiosis • Now we’ve recombined; how to separate? • When is a cell haploid? • Select a gamete, go fuse with a classmate • Stop by and show me the genotype Meiosis • Diversity? • Two chromosomes with recombination • How many possibilities? Meiosis • Crossing Over is GREAT for genetic diversity!!! • What are the ‘costs’? Things go wrong during Meiosis • • • • Non-disjunction Insertion Deletion Inversion Meiosis Clean Up No, we’re NOT done More Vocab… • We’ve talked about chromosomes, mitosis, and meiosis… • Recombining genes via Crossing Over • How likely do you suppose it is that genes are inherited together? More Vocab… • Linkage’ - referring to whether genes are inherited together because they are ‘close’ on a chromosome • ‘Linked’ - referring to the resulting behavior of traits encoded by such genes Gameter • Open Gameter • Move things around, work with the buttons • Notice A and a go together • End up with: ‘A’ and ‘B’ on Chrm II, with A farther right than B • Ab and AB Gameter • Explore – One meiosis – 200 meioses – Move ‘em around and try again • • • • Observe Hypothesize Test Evaluate Disease Presentation Research Project Where we’re headed • Your proposal is an answerable, interesting question • It will reflect causation • Follow rubric – choose a proposal Take a look • Onion root tip – make it a squash • Grasshoppers testes Mitosis (with just ONE set of chromosomes) looks like this… Two IDENTICAL DIPLOID cells + Both cells are still DIPLOID because they have TWO chromosome #1s + When they replicate their DNA, each will look just like the parent cell Show Me MEIOSIS (with TWO sets) looks like this… Meiosis 1 + Each of these cells is HAPLOID as it only has ONE set of chromosomes (1 of each; chrm 1 and chrm 2) Meiosis 2 Four DIFFERENT HAPLOID cells Back to the Cell Cycle Cells spend most of their “lives” like this They only look like this after they replicate their DNA in order to divide (mitosis) • HOMEWORK • Proposal!!!!!!!