BIOL2262: Dihybrid Cross - Test the Hypothesized Ratio by using a Chi-Square Analysis - Science Assignment Help

Assignment Task

Online Practical Activity 1: Drosophila melanogaster Virtual Laboratory Introduction 
This practical activity is designed for students to apply the principles of Mendelian inheritance  in experimentation using the fruit fly Drosophila melanogaster. A virtual laboratory will be  used to test hypotheses by selecting fruit flies with different visible mutations, mating them (i.e. performing a genetic cross), and analyzing the phenotypic ratios of the offspring using  Chi-Square analysis. Single gene inheritance patterns using monohybrid and dihybrid crosses,  sex linkage, lethality and gene linkage will be investigated.  
Go to: (Adobe Flash Player is required) 
Understanding the Program: 
1. Start by ordering two wild type flies and mate them. Click on the computer to order flies.  Click ‘Order flies’. Add a female wildtype fly to your shopping cart and a male wildtype fly  to the shopping cart. Click the Shopping cart icon to view and select checkout.  2. Click on the box to unpack the flies and add them to the mating jar and incubator. 3. Click on the mating jar to place it in the incubator to start the mating. Click on the mating jar to prepare the offspring flies for viewing under the microscope 2. View your flies under the microscope and sort them. 
3. View the flies close-up and note the difference between males and females. 4. Add your data to your notebook. 
5. Use the computer to "analyze results" 
6. Go to the chi square analysis. Enter your hypothesis. Since both of your parents with wild  type, you would expect a 50:50 ratio of male to females. You will need to you a calculator to  determine the expected numbers from the total number of offspring you have. Enter that  number in the "hypothesis" column. 
7. The computer will do the chi square analysis for you and show your statistical results. 8. Return to your notebook and look at your data. 
9. "Save" your notebook. 
Just play with the simulator for now to see what it does. Remove all your data from your  notebook before you start the real assessment.
Part A: Perform a monohybrid cross 
Choose ONE of the following autosomal traits: 
Apterous 
Black Body 
Brown Eyes 
Curved Wings 
1. Choose ONE trait from the autosomal mutations on the table to study by ordering flies of  the mutant strain and crossing it with a wild type fly. 
2. Cross your flies (P generation) and determine the phenotype of the F1 generation. 
3. Now mate the offspring (F1) from that cross together (this ‘self’ cross creates the F2  generation). You can do this by selecting "use fly in new mating" when viewing flies under the microscope view (zoomed out). 
4. Sort your F2 flies and analyze the results. You can choose to ignore sex here, since you know  you are studying only autosomal mutations.  
5. Run a chi-square analysis on your F2 flies (again you can ignore sex). 
Part B: Perform a reciprocal cross to analyze sex-linked traits 
Online Practical Activity 1 
2. Determine how the offspring differ depending on which parent had the mutant phenotype.  Be prepared to explain why this happens in your final lab report. You only need to look at the  F1 generation here. 
3. Test the hypothesized ratios by using a chi-square analysis. 
Part C: Perform a dihybrid cross 
1. Select any two traits on two different chromosomes (autosomes) and study their inheritance  patterns (See chromosome map on page 1). Also be sure that you do not pick any traits that are  lethal or sex linked (see chromosome map for lethal alleles and genes on I-X). 
2. Cross a double mutant with a wild type. Observe the F1 offspring.  
3. ‘Self’ cross an F1 offspring with another F1 offspring to generate the F2 generation. What  Mendelian ratio would you expect in a dihybrid ‘self’ cross?  
4. Test the hypothesized ratio by using a chi-square analysis. 
Part D: Perform a cross to analyse gene linkage  
1. Select two traits on the same chromosome (autosome) and study their inheritance patterns  (exclude sex-linked and lethal mutations, see chromosome map). Choose traits that are less  than 20 map units apart. 
2. Cross a double mutant with a wild type. Observe the F1 offspring.  
3. ‘Self’ cross an F1 offspring with another F1 offspring to generate the F2 generation.

4. Test the hypothesized ratio by using a chi-square analysis.