Worksheet 4.1 Part 3 DONE PDF

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MODULE 4 Worksheet 4.1, Part 3: Exercise 2 Level 1 (30pt)

Name: _Joseph Wassell

Fruit Fly Exercise 2- Level 1 (30pt) Getting started with StarGenetics • To get to StarGenetics, navigate to: http://web.mit.edu/star/genetics/ • Click on the Start button to launch the application (may appear as an icon on your desktop). • Click Trust if a prompt appears asking if you trust the certificate. • Click on File New in the drop-down menu in the upper left-hand corner. • Click on the Fruit Fly Exercise 2-Level 1 file. You have been working with Drosophila melanogaster flies. By now, you are familiar with wild type flies and know that they have red eyes. In one of your fly vials, you discover a male fly with orange colored eyes. You are intrigued since you have never seen a fly with such an unusual eye color. You call this mutant “Orangeye”. You decide to do some genetic analysis of this unusual mutant. To do this, you set up a cross between the Orangeye mutant and a wild type female (scroll down to find these).  

Drag the Orangeye mutant and the wild type female to the Mating site. Click on the Mate button.

1. Describe the progeny that results from this cross (complete the table below):  Each resulting offspring can be viewed by clicking on the Individual tab or a summary of the results is available in the Summary tab Question (1pt) Number of flies that look like the wild type parent: Number of flies that look like the Orangeye parent: Total number of progeny

Your Answer 50 0 50

2. Based on these results… a. Does the mutant allele that confers Orangeye appear to be dominant or recessive relative to wild type? (1pt) ☐ Dominant ☐ Recessive b. How can you tell? (Note: You can use the Punnett Square tool to help decipher genotypes for a given trait. In the Punnett Square tool click on the different genotypic options to see the resulting genotypic ratios) (0.5pt) It is recessive because it would be impossible for the orangeye trait to be dominant and receive 0 orange-eyed offspring

MODULE 4 Worksheet 4.1, Part 3: Exercise 2 Level 1 (30pt)

Name: _Joseph Wassell

3. You intended to separate the F1 males from the F1 females (from the cross in question 1, above) as soon as they emerged. Unfortunately, school closes due to a snowstorm and by the time you get back to your flies, you find that the F1 flies have emerged and mated! You decide to make the best of it and analyze the F2 progeny obtained from this cross. While you wait for the F2 larvae to mature into flies, you decide to predict what F2 progeny will result from this cross. Show your predictions below (before using StarGenetics to perform the cross) and indicate the genotypic and phenotypic ratios that you expect. Your predictions should be based on your answers to questions 1 and 2. (2pt) P1 cross: Orangeye ♂ (genotype? ____ee______ ) x wildtype ♀ (genotype? __EE_______ )  F1 progeny:

F1 cross:

genotype? ___Ee_______ (results from table in question 1)

F1 ♂ (genotype? ____Ee______ ) x F1 ♀ (genotype? ___Ee_______ ) 

F2 progeny: E

e E

EE

Ee

Ee

ee e

Expected genotypic ratio: ______1EE:2 Ee:1 ee________ (1pt) _______3 red eyed:1 orange eyed______ (1pt)

Expected phenotypic ratio:

4. Now go ahead and actually mate an F1 female to an F1 male in StarGenetics.  

To start a new mating click on the Save experiment button. Perform mating as previously described.

a. What results do you observe? Indicate the phenotypic ratios from this cross. (1pt) It appears that 1/5 are orange eyed flies. Also, all of the orange eyed flies are male. Phenotypic ratio- 4 red eyed:1 orange eyed

MODULE 4 Worksheet 4.1, Part 3: Exercise 2 Level 1 (30pt)

Name: _Joseph Wassell

b. Do the results match your predictions? Please explain. (1pt) These results somewhat match the predictions made. I predicted the ratio to be 3 WT:1 mutant and it turned out to be 4 WT:1 mutant. The red eye phenotype (WT) occurred more than the orange eye phenotype (mutant).

c. Is there an approximately even distribution of all phenotypes between male and female flies? (0.5pt) No, all the orange eyed flies were males.

d. Given your answer in (c), what hypothesis could explain the phenotypic ratios you observe for the F2 generation? (1pt) This could be a y-linked trait, meaning that only males can be affected. This could be proved by mating a mutant F2 male with a WT F2 female since y-linked traits do not skip generations.

e. Explain your reasoning by showing Punnett squares for both the P1 (2pt) and F1 (2pt) crosses below: P1 cross:

Orangeye ♂ (genotype? _____ ee_____ ) x wildtype ♀ (genotype? ____ EE______ )  

F1 progeny:

E

E

Ee

Ee

Ee

Ee

e

e F1 progeny:Phenotype of ♂ progeny? _____________ All red eyes__________________________ (1pt) Phenotype of ♀ progeny? ______________All red eyes_________________________ (1pt)

F1 cross:

F1 ♂ (genotype? ___Ee_______ ) x F1 ♀ (genotype? ____Ee______ ) 

F2 progeny: E

e E

MODULE 4 Worksheet 4.1, Part 3: Exercise 2 Level 1 (30pt)

F2 progeny:

Name: _Joseph Wassell

EE

Ee

Ee

ee

Phenotype of ♂ progeny? (1pt) 1/5 orange eyed and 4/5 red eyed Phenotype of ♀ progeny? __All red eyed________ (1pt)

5. You share your unusual results from question 4 with a friend who is also studying genetics in a Drosophila lab. She tells you that she has a fly strain with another mutant eye color, white. Your friend gives you a female fly, Whiteye, from her true-breeding white-eyed fly stock. She also tells you that the mutant allele that confers white eyes in this strain is recessive to wild type. a. Set up a cross between Orangeye and Whiteye. Based on the results you obtain (and your understanding of gene complementation), indicate whether the mutations in Whiteye and Orangeye are in the same gene or in different genes (1pt). Explain your answer (1pt). ☐ Whiteye and Orangeye are mutations within the same gene -->☐ Whiteye and Orangeye are mutations in different genes (i.e. at separate gene loci) Rationale for your answer: The resulting cross gave 100% WT phenotypes (red eyes). The mutations for orange and white eyes are on different genes because the orange mutation on one chromosome complimented the mutation for white eyes on another chromosome and reverted the phenotype back to the WT standard. If a mutant x mutant cross gives you progeny with restored WT phenotype, it is said that the mutations compliment each other.

6. After completing your analysis with the orangeye mutant, you decide to determine whether the mutation that confers white eyes in the Whiteye mutant is found on the X chromosome or on an autosomal chromosome. a. Using the Whiteye mutant and wild-type flies, perform the following 2 experiments, first to test if Whiteye is on the X chromosome, then to determine if Whiteye is on an autosome: If Whiteye is a gene on the X chromosome… the Punnett square (below) would describe the expected F1 progeny: (2pt) P1 cross: ♂ (phenotype? __ Red eyes______ genotype? _EE ____) x ♀ (phenotype? _white eyes_______ genotype? _ee____) 

MODULE 4 Worksheet 4.1, Part 3: Exercise 2 Level 1 (30pt) F1 progeny:

Name: _Joseph Wassell E

E e

Ee

Ee

Ee

Ee e

F1 progeny: Phenotype of ♂ progeny? _____________white (due to xrecessive affecting males more, any affected female will give it to ALL her

linked sons)_ (1pt)

Phenotype of ♀ progeny? ______________white and red (it the female progeny received the mutated x-chromosome) (1pt)

depends if

If Whiteye is a gene on an autosome… the Punnett square (below) would describe the expected F1 progeny: (2pt) P1 cross: ♂ (phenotype? ___red eyes_____ genotype? __ _EE__) x ♀ (phenotype? __white eyes______ genotype? _ee____)  F1 progeny:

E

E e

F1 progeny:

Ee

Ee

Ee

Ee

e

Phenotype of ♂ progeny? ____Red eyes(1pt) Phenotype of ♀ progeny? (1pt) Red eyes

b. Based on your predicted crosses above and the data you received from setting up the crosses, is the mutation that confers white eyes in the Whiteye mutant found on the X chromosome or on an autosomal chromosome? Explain your answer. (2pt) ☐ Whiteye is a gene found on the X chromosome ☐ Whiteye is a gene found on an autosomal chromosome 

MODULE 4 Worksheet 4.1, Part 3: Exercise 2 Level 1 (30pt)

Name: _Joseph Wassell

Rationale: I think it is on an autosomal chromosome because if it were on an x chromosome, then the affected female would pass that trait on to ALL of her sons and when I ran the experiment on StarGenetics, no males (or females) had the trait. While both alleles are mutated in the mother (which is a requirement of autosomal recessive traits), the WT father is homozygous dominant so all of their progeny will receive one big E allele, meaning that none of their kids will receive two mutated recessive alleles....