Did Mendel fake is data? Do a quick internet search and can you find opinions that support or reject this point of view. Does it matter? Should it matter?

Slides:



Advertisements
Similar presentations
General Genetic Bio 221 Lab 6. Law of Independent Assortment (The "Second Law") The Law of Independent Assortment, also known as "Inheritance Law", states.
Advertisements

Virtual Fly Lab AP Biology
AP Biology.  Segregation of the alleles into gametes is like a coin toss (heads or tails = equal probability)  Rule of Multiplication  Probability.
Mendelian Genetics. Genes- genetic material on a chromosome that codes for a specific trait Genotype- the genetic makeup of the organism Phenotype- the.
Chi-Square Test A fundamental problem is genetics is determining whether the experimentally determined data fits the results expected from theory (i.e.
UNDERSTANDING LINKAGE, AND GENETIC MAPPING. INTRODUCTION Each species of organism must contain hundreds to thousands of genes Yet most species have at.
Laws of Probability and Chi Square
Chi-Square Analysis Mendel’s Peas and the Goodness of Fit Test.
1 Review What is probability Use Models How are Punnett squares used to predict the outcomes of genetic crosses 2 Review What is independent assortment.
Incomplete dominance. Incomplete dominance Polygenetic Ex. Human skin color.
What is a χ2 (Chi-square) test used for?
Chi Square Analyses: Comparing Frequency Distributions.
Chi-square notes. What is a Chi-test used for? Pronounced like kite, not like cheese! This test is used to check if the difference between expected and.
Chi-Square Test A fundamental problem in genetics is determining whether the experimentally determined data fits the results expected from theory (i.e.
Chapter 11 Section 2 Applying Mendel’s Principles
Applying Mendel’s Principles Probability, Punnett Squares, & Independent Assortment (Dihybrid Cross) Section 11.2.
11.4 Hardy-Wineberg Equilibrium. Equation - used to predict genotype frequencies in a population Predicted genotype frequencies are compared with Actual.
Chi Square.
Chi-Square as a Statistical Test Chi-square test: an inferential statistics technique designed to test for significant relationships between two variables.
Chi-Square Test A fundamental problem in genetics is determining whether the experimentally determined data fits the results expected from theory. How.
Chi square analysis Just when you thought statistics was over!!
Chi Square Analysis The chi square analysis allows you to use statistics to determine if your data “good” or not. In our fruit fly labs we are using laws.
Chi-Squared Genetics and Statistics A Tale of Two Hypotheses.
Statistical Analysis: Chi Square AP Biology Ms. Haut.
Chi-Square Analysis AP Biology.
16 Box Punnett Squares and Mendel’s Laws Using a Chi-Square Analysis to study inheritance patterns.
Analyzing Data  2 Test….”Chi” Square. Forked-Line Method, F2 UuDd x UuDd 1/4 UU 1/2 Uu 1/4 uu 1/4 DD 1/2 Dd 1/4 dd 1/4 DD 1/2 Dd 1/4 dd 1/4 DD 1/2 Dd.
Section 2: Mendelian Genetics
The Chi Square Equation Statistics in Biology. Background The chi square (χ 2 ) test is a statistical test to compare observed results with theoretical.
III. Statistics and chi-square How do you know if your data fits your hypothesis? (3:1, 9:3:3:1, etc.) For example, suppose you get the following data.
Chi Square Pg 302. Why Chi - Squared ▪Biologists and other scientists use relationships they have discovered in the lab to predict events that might happen.
In the broad bean, a pure-breeding variety with green seeds and black hilums (the point of attachment of the seed to the pod) was crossed with a pure breeding.
AP Biology Heredity PowerPoint presentation text copied directly from NJCTL with corrections made as needed. Graphics may have been substituted with a.
Chi-Square (χ 2 ) Analysis Statistical Analysis of Genetic Data.
Chi-Square Analysis AP Biology.
The Chi Square Test A statistical method used to determine goodness of fit Chi-square requires no assumptions about the shape of the population distribution.
Chi-Square Test A fundamental problem is genetics is determining whether the experimentally determined data fits the results expected from theory (i.e.
Chi-Squared Χ2 Analysis
Virtual Fly Lab AP Biology
Chi-Square Test A fundamental problem is genetics is determining whether the experimentally determined data fits the results expected from theory (i.e.
Cell Cycle and Chi Square
6.5 Traits and Probability
Analyzing Data c2 Test….”Chi” Square.
Virtual Fly Lab AP Biology
Chi-Square Analysis AP Biology.
The Chi Square Test A statistical method used to determine goodness of fit Goodness of fit refers to how close the observed data are to those predicted.
Chi Square SBI3UP.
And Yet more Inheritance
Analyzing Data c2 Test….”Chi” Square.
The Chi Square Test A statistical method used to determine goodness of fit Goodness of fit refers to how close the observed data are to those predicted.
Analyzing Data c2 Test….”Chi” Square.
Chi-Square Analysis.
Topic 10.2 Inheritance.
Chi Square Analysis The chi square analysis allows you to use statistics to determine if your data is “good” or not. In our fruit fly labs we are using.
Genetic Mapping Linked Genes.
Chi-Square Analysis AP Biology.
Statistical Analysis Chi-Square.
Corn Genetics Lab: Notebook Format
The Chi Square Test A statistical method used to determine goodness of fit Goodness of fit refers to how close the observed data are to those predicted.
Chapter 6: Introduction to Genetics
Chi-Square Analysis AP Biology.
Chi-Square Analysis AP Biology.
UNIT V CHISQUARE DISTRIBUTION
S.M.JOSHI COLLEGE, HADAPSAR
Completion and analysis of Punnett squares for dihybrid traits
THE CHI-SQUARE TEST JANUARY 28, 2013.
Chi-Square Test A fundamental problem in Science is determining whether the experiment data fits the results expected. How can you tell if an observed.
Chi-Square Analysis AP Biology.
Presentation transcript:

Did Mendel fake is data? Do a quick internet search and can you find opinions that support or reject this point of view. Does it matter? Should it matter?

Does the data fit? Problem: Does experimentally determined data fits the results expected from theory (i.e. Mendel ’ s laws as expressed in the Punnett square). Example: –Expected 75% to 25% ratio –Does an observed result of 78 to 22 fit?? 85 to 15?

The Chi Square Test A “ Goodness of fit ” test A statistical way to “ Reject the Null Hypothesis ”

Null Hypothesis A way to state expected outcome Example 1: Hybrid parents will produce a 3:1 genotypic ration (predicted values based on punnett square analysis) Example 2: Flipping a coin should land on heads 50% of the time. **Chi-square is used to REJECT a hypothesis not to PROVE it.

Coin Data If this coin is fair…then we would expect the chi-square analysis to show us the results are due only to chance and not due to some other hypothesis. Let ’ s look how coin data either: –Rejects a hypothesis that a coin is fair or –Suggests that the hypothesis that a coin is fair is likely.

The Formula

Example Expected results of a coin toss (the Null Hypothesis): 50 heads, 50 tails Observed results: 55 heads, 45 tails Now it's just a matter of plugging into the formula:  2 = ( ) 2 / 50 + ( / 50 = (5) 2 /50 + (-5) 2 / 100 = 25 / / 50 = = 1.0 This is our chi-square value: now we need to see what it means and how to use it.

Chi-Square Table

Using the Table In our example of 55 heads to 45 tails, we calculated a chi-square value of 1.0, with 1 degree of freedom. Looking at the table, 1 d.f. is the first row, and p = 0.05 is the sixth column. Here we find the critical chi-square value, Since our calculated chi-square, 1.0, is less than the critical value, 3.841, we “ fail to reject ” the null hypothesis. Thus, an observed ratio of 55 heads to 45 tails is a good fit to 50:50 ratio.

Degrees of Freedom A critical factor in using the chi-square test is the “ degrees of freedom ”, which is essentially the number of independent random variables involved. Degrees of freedom is simply the number of classes of offspring minus 1. For our example, there are 2 classes of offspring: heads and tails. Thus, degrees of freedom (d.f.) = 2 -1 = 1.

Critical Chi-Square Critical values for chi-square are found on tables, sorted by degrees of freedom and probability levels. Science uses p = If your calculated chi-square value is greater than the critical value from the table, you “ reject the null hypothesis ”. If your chi-square value is less than the critical value, you “ fail to reject ” the null hypothesis (that is, you accept that your genetic theory about the expected ratio is correct).

Corn and Chi-Square for Real Question: Is this corn the result of the following dihybrid cross: PpSs X PpSs -First do the Punnett Square -Find the expected outcomes -Compare actual to expected by doing chi square. Share your results with a nearby group.

Lab Notebook Expectations Introduction: How does the dihybrid cross show Mendel ’ s Law of Independent Assortment? Identify the traits you will be looking at in the corn. Hypothesis: What do you expect from crossing two heterozygotes—may show a Punnett Square. Methods: How did you count a random sample of the corn? What does each kernel on the corn represent?

Data and analysis: -Chi-square analysis for your data. -Chi-square analysis for another group ’ s data. -Trend related to each chi-square analysis. Conclusion: -Explain how the chi-square analysis can confirm Mendel ’ s Law of Independent Assortment. -Discuss what genetic linkage is and why this would cause you to reject the null hypothesis shown in a dihybrid cross.

Practice How can Chi- square be used to analyze these results?

Back to problem set #21 Go back to the genetic recombination problem…do a chi- square analysis as if it was not linkage. What does your analysis tell you?

Do Mendel ’ s laws always apply? Dominance Segregation Independent Assortment

Questioning Mendel ’ s Peas If all his data made sense, what can we say about the genes he looked at: were they on the same chromosome or on different chromosomes?

A quick review of genetic material…. Chromosome Chromatin DNA Gene Nucleotide Nuclear proteins? Does the location of a gene affect inheritance patterns?

Genes are linked to chromosomes

Crossing-over Cross-overs occur when tetrads form during meiosis Recombination frequencies allow for the creation of chromosome maps

Recombination due to cross-overs

Recombination frequencies

Chromosome map

Sex-link chromosomes Genes located on the X or Y chromosomes are linked to gender What observation provide hints that a gene is sex linked?

Example: Eye Color in Fruit Flies