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Lab 8: Meiosis & Phenotype Taking care of genetic information; figuring it out from a standing start Meiosis & Phenotype Today we’ll: • Refine problem-solving skills • Explore all strategies & outcomes to determine the best one – And save hours on homework Today… • We will figure out the dominant trait and genotype for a set of individuals • There will be no luck, no guessing needed • We will generate and explore all (simple) hypotheses and rule out those that do not fit, until only one viable one remains Thinking it Through • Develop lines of ‘pure breeding’ traits (green and yellow peas) • Cross them… ONLY yellow trait is evident – TWO hypotheses? – One test? Thinking it Through • Two Hypotheses • Make a prediction – IF ‘this’ is true, THEN… • Model and test Scaling • A gene is ~1,000-100,000 basepairs* • A chromosome is tens or hundreds of thousands of genes *Includes control regions & stuff that won’t make it into the final product Vocab Revisited • 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! • Genotype/phenotype: Underlying cause; outward appearance Pheno to Geno Deducing the latter from the former Working Through • Which traits are dominant? What are individual genotypes? You can use sex to find out! • Today we’ll engage in some specific problemsolving techniques • • • • Combinatorial thinking Enumerating hypotheses ‘Last one standing’ Orderly approaches & record keeping Vocab and Symbols • Allele: A version (or flavor) of a gene; two alleles of the same gene my differ by a nucleotide or dozens of them – Common symbolism: B vs b or BLU vs blu • Homozygous: ‘same pairing’ = has identical alleles (AA, aa) • Heterozygous: ‘different pairing’ = has different alleles (Aa) What’s Dominant? • Imagine you are confronted with two phenotypes (color) • Can you tell which is dominant? • What crosses should you do to quickly assign dominance & genotype? http://talkbudgies.com/showthread.php?t=41797 Occam’s Razor? • What? • “No more things should be presumed to exist than are absolutely necessary.” • So, how many alleles should we assume, and what sort of relationship? Remember When? • Where do sperm and eggs come from? (Process) • How many alleles for each trait/gene in each gamete? – How to distribute? • When doing Punnett squares, what do the ‘letters’ represent? Today we’ll… • How many blue-budgie genotypes in a ‘blue-budgie’ dominant world?” • What do your offspring look like from blue x blue? • Ways to make green in a ‘blue’ world? • What if it’s a ‘green-budgie’ dominant world • Develop a sure path to the budgie genotypes regardless of which ‘world’ How will you know what’s dominant? • Two hypotheses? Blue is dominant vs Green is dominant • First: Blue Dom – which genos => dominant appearance (pheno.) • Recessive phenotype? • All possible blue x blue in Blue world? • All possible green x green in Blue world? How will you know what’s dominant? • Two hypotheses? Blue is dominant vs Green is dominant •What First: Blue Dom – which => crosses yieldgenos all blue? dominant appearance All green? • Recessive phenotype • All possible blue x blue in Blue world? • All possible green x green in Blue world? More Punnetts • Keep your blue work • Start ‘again’ in a Green dominant World Whatcha got? • How explanatory are these crosses? • Anything useful? • How useful to cross to ‘same’ organisms? – ‘need’ heterozygotes • If same X same not working, what should we explore? A better way? • Need more room? Open x_plorer • Graded exercise – show me ‘Total Victory’ and explain what/why you won (100% or 0%) MORE Vocab • Naming is hard. Your parents are their parents’ children. So what’s a parent & what’s a child? • In x_plorer: parents stay parents • Formally, you will hear P1, F1, F2 in crosses • P1: the initial parents for the events in question • F1: First filial (of pertaining to, or benefiting a son or daughter) • F2: Second filial x_Plorer • An exercise to guide you in thinking • Simultaneously consider two alternative hypotheses about dominance (left half; right half) • Work through BOTH cases until you have an ordered set of tests (algorithm) to distinguish (i.e. rule one OUT) • Watch the lavender box for ‘what to do next’ x_Plorer • If you cross Blue with Red and get… • Then…. Lab Instructor: Why ‘Total Victory’ ? How ‘good’ is the Interweb? “The genetics of dimples is actually rather interesting. Dimples are a dominant trait, which means that it only takes one gene to inherit dimples. If neither of your parents has dimples, you shouldn't have them either, unless you experience a spontaneous mutation. If one of your parents has dimples, you have a 25-50% chance of inheriting the gene, since it means that parent inherited the gene from one or both parents. If both of your parents have dimples, you have a 50100% chance of inheriting the gene, depending on how they inherited their dimple genes.” What do you have? IF… THEN http://www.wisegeek.com/what-are-dimples.htm How ‘good’ is the Interweb? “The genetics of dimples is actually rather interesting. Dimples are a dominant trait, which means that it only takes one gene to inherit dimples. If neither of your parents has dimples, you shouldn't have them either, unless you experience a spontaneous mutation. If one of your parents has dimples, you have a 25-50% chance of inheriting the gene, since it means that parent inherited the gene from one or both parents. If both of your parents have dimples, you have a 50100% chance of inheriting the gene, depending on how they inherited their dimple genes.” http://www.wisegeek.com/what-are-dimples.htm Phenos to Genos NOW the fun!!!! MendelStar! • Given the outcome, can you predict the genotype of the parents? • Observe, Hypothesize, Predict, Model/Test • Have a plan • Write it down MendelStar! • For practice purposes, use the ‘Just Mendel’ option • If NOT logged in, tutorial in main lab walks you through ‘mating and sorting’ (Show Me... menu) • If all that color & such is bugging you, use the ‘Image Simplify’ menu to focus on 1 trait • When not logged in, go to the ‘Evaluate’ destination for a list of the genotypes in play Mate your own Butterflies! • Once logged in, choose ‘Find the Genotype’ • Work through problems – Have a plan – Write it down! (IF this is TRUE…) – Saves time! • After answering, hit submit; if score < 76 you’ll get a hint • You can store at any time by submitting Mate your own Butterflies! • Why 76 points ‘max’? • Yep, written part in dropbox • Really, have a plan Part 5 of Presentation • Due next week in dropbox Meiosis & Phenotype