Lecture 3 - Mendelian Inheritance Part I 1 Last Time...

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Unformatted text preview: Mendelian Inheritance Part I 1 Last Time Scientific Methods Hypothesis-driven science What's in a Paper? Intro to Paper Bashing 2 Mendelian Inheritance Part I Mendel's contribution to Genetics Why peas?! The mono-hybrid cross The di-hybrid cross Fundamental principles of genetics A quick look at Mendel's hallmark paper 3 Ideas about inheritance before Mendel (~400 BCE) Hippocrates and the seeds (1665) Nicholas Hartsoeker and the little man (homunculus) (1761) Joseph Kolreuter and blending inheritance FROM JULIA STONEHOUSE (1994) FROM IDOLS TO INCUBATORS 4 Mendel (1822 1884) Developed model to predict the inheritance of traits mathematical (quantitative approach) scientific method variation in traits 5 Why peas? Easy to grow and manipulate Obvious variation in traits Clear phenotypes (white petals vs. purple petals) 6 Clear phenotypes 7 Mendel's fortuitous decisions Studied `either-or' characteristics not `more or less' Began with `true breeding' plants Controlled breeding of plants Large sample sizes Accurate records 8 The Big Question How are traits inherited? Two models: Blending vs. Particulate model of inheritance EMPTYEASEL.COM/WP-CONTENT/UPLOADS/2006/12/GREEN.JPG 9 The Experiments PARENTAL (P) generation: FILIAL (F)1 generation: FILIAL (F) 2 generation: 705 224 10 Some Data Tall x dwarf stem F1 = all tall, F2 = 787 tall, 277 dwarf Purple x white flowers F1 = all purple, F2 = 705 purple, 224 white Yellow x green seeds F1 = all yellow, F2 = 6022 yellow, 2001 green 11 Terms CAPITOL LETTER = dominant behavior ex. T for tall lower case letter = recessive behavior ex. t for dwarf TT tt PP pp 12 Punnett Square - a model for predicting alleles in offspring F1 Sperm F1 Eggs F2 generation 13 Random fertilization will lead to four possible outcomes F1 Sperm F1 Eggs P = purple p = white 14 F2 generation Summary 15 A Review of Terms 16 The test cross What is the genotype of this flower? the test cross determines the genotype of a parent Option 1: if PP x pp (white) - results? Option 2: if Pp x pp (white) - results? 17 Law of segregation Alleles of a gene separate from each other during transmission from parent to offspring F1 Sperm F1 Eggs F2 generation 18 Do alleles for two genes (ex. seed color and seed shape) sort into gametes together or independently? 19 Predicted outcomes DEPENDENT ASSORTMENT 1/2 1/2 Sperm Eggs F2 Generation (predicted offspring) 1/2 INDEPENDENT ASSORTMENT 1/2 Phenotypic ratio 3:1 20 Law of Independent Assortment Two different genes will assort their alleles during the formation of haploid cells 21 The Big Question How are traits inherited? Two models: Blending vs. Particulate model of inheritance EMPTYEASEL.COM/WP-CONTENT/UPLOADS/2006/12/GREEN.JPG 22 Experiments in Plant Hybridization (1865) Format Question addressed Experimental design Use of controls Mendel's view of evolution? WWW.LIBRARY.VILLANOVA.EDU 23 Summary Gregor Mendel used math and scientific methods to study inheritance Addressed mechanism of inheritance of traits Law of segregation - the two alleles end up in different gametes Law of independent assortment - two genes sort into gametes independently of one another 24 Ungraded Problems (to do on your own) Chapter 2: Read over S3 (illustrates common mistake) Chapter 2: C4 - C8* Make sure you know how to do Punnett Squares, know the Laws of Inheritance, Mendel's influences and contribution * answers are online or in optional Genetics Study Guide 25 Next Time Mendelian Inheritance Pt 2 FLICKR PHOTO COURTESY: LA TARTINE GOURMANDE 26 ...
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This note was uploaded on 10/13/2009 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas at Austin.

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Lecture 3 - Mendelian Inheritance Part I 1 Last Time...

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