Nice animation, includes recombination

Announcements Genetic Disease Presentations – sign up for a date Proposals graded – see comments and revise! Come to me with any questions regarding revision of proposals after class today All hemoglobin tutorials graded, see comments and answer key. Downloadable from course software page 2

Comments on Citations You MUST cite any information used from an online website, textbook or the lab manual EVEN if you put it in your own words Review citation format (journal of Ecology example) 3

Citation Example Last initial. First name. (Year). Title of article. Journal. Volume:page numbers. Example: S. John, B. Anne, and R. Jordan. (2012). Assessing the effects of spatial contingency and environmental filtering. Ecology. 93: In text (Author last name, year) Example from above citation: (Smith et al., 2012). If more than two authors – et al., after first author (note: must state all authors in citation at the end of the document, et al. is only for in text) If two authors, state both last names with ‘and’ in between In text – superscript  after use of information from article, superscript the number of the citation as it appears in the citation list at the end of the document 4

5 Dividing & Delivering Distributing genetic information How?Why?

6 Goals for today Scaling: Nucleotide, Gene, Chromosome--and how many of each Concept: Chromosomes are hugely long threads of DNA; some regions are genes PURPOSES of ‘mitosis’ & ‘meiosis’ & how these dictate the events Mixing and matching parental DNA made you. It provides hope you’re better than them ;)

7 The birthday cake gene You are a birthday cake-making company! A call comes in to order a cake. What information must you take? You’re an old fashioned mom-and-pop place; no photos

8 Scaling A gene is ~1, ,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 *Includes control regions & stuff that won’t make it into the final product **We keep finding stuff that matters

9 Blinding you with Science (jargon) Gene: A stretch of DNA that represents all the 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! More in the lab manual & Vocab exercises!

10 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?

11 Ripped from the 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, suggesting single origin Headline: Blue eyes result of ancient genetic ‘mutation’ Headline It’s not a ‘mutation’; it’s a mutation [FYI]: On green eyesgreen eyes

12 Touching mitosis & meiosis

13 Meet the Chromosomes Compare our bead models with image What corresponds?

Some data on PTC, hair, etc. (Source: Exploring Biology in the Laboratory, p ) USE these to make the point that dominant <> predominant (and to give everybody a break in which they think about their own phenotypes) PTC paper: 70% can taste; tasting is dominant (SAVE for Pedigrees) Bent little finger: bending inwards towards ring finger is dominant Tongue rolling--ability to roll is dominant Widow's peak--v-shaped hairline (think Paul Ryan). Means you are Devil's spawn, is dominant Dimpled chin--Dominant to have the dimple Free earlobe: port is detached. Detached = dominant Swing hands, clasp together. If left thumb over right, you've got the dominant trait Bending your thumb away from your palm: INability to bend tip 60 degrees relative to thumb is dominant Hair on middle joint of finger is dominant Dimpled cheeks is dominant Ability to raise eyebrows is dominant Ability to wiggle ears is dominant second toe longer than big toe? Dominant Curly hair dominant to straight Freckles is dominant

15 Genotype, phenotype Pick two traits Pick a dominant & recessive outcome arising from different alleles You all start off heterozygous

16 Symbolism String of beads = chromosome = double-stranded DNA bead = gene Pay close attention to the nipples!

17 Mitosis Manually 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?

18 Clear your mind Go outside & take a lap around the floor Yeah. Go

19 Meiosis: the other cell division

20 Throwing the dice “Sexual reproduction has been compared to a game of roulette in which the players throw away half their chips at every spin of the wheel.” Jonathan Silverton, ‘An Orchard Invisible’ p. 22

21 Why have sex? Suppose I’m Jack Sprat; you’re my wife. I have the mutant form of the fat-eating gene; you of the lean-eating gene If we reproduce asexually (mitotically), how long until some descendant can eat a whole pig? If sexually, i.e. by taking parts of our holdings & throwing them together in an offspring?

22 Thinking it through How much are you ‘like’ your ma & pa? How much of your genome should you give your child if he/she is not uni-parental?

23 Why bother II-- breaking DNA Just shuffle the chromosomes: all the genes on every chromosome inherited together Recombine between homologs: one set of genes on a chromosome inherited independently of another

24 Homologous Recombination I Where should the circled site on Chromo1 recombine with Chromo2? 1 2 3

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26 Dances with Genes First, make a copy--b/c that’s the way it happens Pair the pairs: duplicated mom’s & dad’s contributions pair Recombine (randomly)

27 Dancing II Now we’ve recombined; how to separate? When you’re a gamete, go fuse with a classmate Stop by and show me the genotype

28 Seeing & Believing Mitosis: Turning an onion into a squash Meiosis: Prepared grasshopper testes

29 Genes on chromosomes

30 Blinding you with Science (jargon) II Linked/Linkage: Referring to whether genes are tethered to one another by virtue of being ‘close’ on a chromosome Linked: referring to the resulting behavior of traits encoded by such genes

31 Think it over... No recombination: every chromosome is a linkage group recombination: new combinations every cross-over (= every gamete)

32 Fire it up Load Gameter Interface walk-through: designing the parentals A & B close together on Chromosome II, A further to the right than B, A/A and b/B

33 Sciencize it! Explore Observe Hypothesize

34 A word on research Tying the papers, the observations & your interests together

35 Where it’s heading You’ll propose an answerable, interesting question It will reflect a causal view of the universe (i.e. not ‘does it go left or right if I...’ but ‘since simple mazes can often be solved by keeping your left hand on a wall, I hypothesize that the organism will have an innate leftward bias that will manifest if I...’

36 Clean up

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38 Homework Gameter: 4 challenges worth 80 pts Written portion worth 20 pts – see rubric