Introduction to Genetics Reading: Freeman, Chapter 13 (read twice, do all the questions at the back of the chapter), also Chapter 12 (to review meiosis, mostly)InformationWHAT IS A GENE?What is an allele?Example:Slide 6Slide 7Slide 8Slide 9Slide 10MitosisSexual ReproductionDiploidyMeiosisSlide 15Errors in MeiosisHow Meiosis, and Sex, Produce VariationSlide 18Slide 19The Patterns Inherent in Mendelian Genetics Result from the Nature of the Eukaryote Genome, and the Events of MeiosisVariation is ubiquitous, all organisms exhibit SOME variationSlide 22Types of VariationDistributions of ValuesA HistogramTypes of DistributionsNormal DistributionA Skewed DistributionBimodal DistributionMean, Median, Variance, etc.DominanceSlide 32Some Alleles of Medical InterestSlide 34CodominanceHuman Blood TypeSlide 37Phenotype vs. GenotypeHow Many Loci are There?Genes Interact with the Environment to Produce a PhenotypeGeographic Variation in Yarrow-A Norm of ReactionSlide 42Genetics ProblemSlide 44Much of what we know about genes was first discovered by Gregor MendelMendel’s LawsA Classic Mendelian ExperimentSlide 48Questions:Answers:Another ExperimentIndependent AssortmentSlide 53Slide 54Sample ProblemSlide 56SOLUTION:Slide 58Now, imagine two of their children interbred and had a child.Slide 60Punnet Square:Slide 62QUESTIONANSWER:Testing Independent AssortmentTest CrossTest Cross RatiosThe Chi-Square Test:This is how we would do a Chi-Square test:Answer:What the #@!?? Does this Number Mean?Slide 72Slide 73Most scientists use an arbitrary criterion to determine whether the departure of observed and expected values was due to chance, or due to a flaw in the hypothesis that generated the expected values to begin with.Slide 75LinkageExample of LinkageAnswer:Now, imagine we got this dataAre the loci linked?Slide 81Slide 82Linkage MappingSlide 84Slide 85An Interesting System, Heterostyly in PrimroseSlide 87Slide 88Slide 89Sex-LinkageSlide 91Slide 92A Genetic Cross With Sex LinkageSlide 94Slide 95Slide 96X inactivationSlide 98EpistasisCoat Color in MiceQuestion: A BROWN mouse is mated to a WHITE mouse. All of the resulting offspring are BLACK. What is the genotype of the offspring? What types of gametes can they produce?Slide 102Question:Answer.Pleiotropy:Penetrance and ExpressivityIntroduction to GeneticsReading: Freeman, Chapter 13 (read twice, do all the questions at the back of the chapter), also Chapter 12 (to review meiosis, mostly)Information-Genetics is, quite simply, the study of the process by which information is transmitted from one generation of living things to the next.-Every living thing is organized via coded information, called its genetic material.-Reproduction involves duplication and transmission of an organisms genetic material.WHAT IS A GENE?A gene is an information entity. It is a sequence of DNA that codes for a single genetic instruction. Usually, this instruction is the sequence of a protein, but a gene may also serve to activate or deactivate other genes, in a cell, or in neighboring cells.Every aspect of our species is constructed based on information encoded in genes.The genes themselves do very little, they are information storage molecules. It is the cytological machinery of our cells, passed from one generation to the next, that translate these instructions into a living organism.The effects of every gene depend both upon other genes, and upon the environment.What is an allele?•An allele is ONE variant of a gene. Many genes have two, several, or many different variants of the same basic genetic information. •Some alleles are minor differences that to not significantly affect the organism, others cause profound changes.Example:•Nucleotide substitutions in the third codon position often produces no change at all, because they code for the same transfer RNA and thus the same protein is produced.•In humans…CCU CCA does not cause a change, both triplets code for proline.•Other substitutions may produce profound effects, sickle cell anemia is caused by a single nucleotide substitution: GAG GUG changes normal hemoglobin to hemoglobin that “sickles” under low oxygen concentrations.-Prokaryotes, which include the archaea and bacteria, are the simplest, oldest, and most common organisms on the planet.-A typical prokaryote has a much smaller genome than a typical eukaryote.-Nearly always, it is in the form of a simple loop of DNA (with associated proteins).-This loop is attached to the cell membrane.-Even though the structure simple, there is a lot of DNA in a single bacterium. .…-Stretched out, the DNA in an E. coli would be 500 times longer than the cell itself.-Prokaryotes do not have sexual reproduction, though they have several forms of gene exchange.-These include swapping plasmids•The various genes, about 1200 in a typical bacterium, are arranged along the length of the chromosome, like beads on a string.–There is no particular functional grouping to their order, it is mostly evolutionary chance that determines their location•In prokaryotes, the DNA loop replicates before fission, with both loops still attached to the cell membrane •During fission, as the cell membrane splits in two, one loop of DNA ends up in each new “daughter cell”Thanks to/stolen from fig.cox.miami.edu-Most eukaryotes have several orders of magnitude more DNA than a typical prokaryote.-Like prokaryotes, eukaryote genes are arranged along the length of a chromosome like beads on a string. -There is no particular functional reason for their location, either within a chromosome, or with respect to what chromosome they are on, it is mostly an evolutionary accident.-Eukaryote DNA (except plastid DNA, which is very similar to bacterial DNA because of its evolutionary origin) is usually linear, not circular.-These strands are long, and extended (thus, invisible to microscopes) during the normal life of the cell.-These linear strands of DNA are called chromosomes and packed into a nucleus (or nuclei, in some cases).-In multicellular eukarotes, every cell has the same DNA, though in any given cell, only a fraction of the genes are active, others are permanently “turned off” during development.-The increased amount of DNA necessitates a means of condensing these long strands into compact structures that can be sorted into separate daughter cells during cell division.-Histones are important and very evolutionarily conservative proteins.