Chemistry Report Corrections

BIOL 105

Experiment to determine the Drosophila genome and Inheritance of both the red-eyed and white-eyed traits (word count 1000)

Name: Mai Alqattan

Instructor: Timothy McClure

Experiment to determine the Drosophila genome and Inheritance of both the red-eyed and white-eyed traits

Mai Alqattan

Abstract Comment by Tim I McClure: The abstract is supposed to have portions of each aspect of the text. You basically have no introduction or discussion, and your results are interpreted incorrectly Also, you need to clearly say what you mean – for example instead of “the values obtained…” you should just tell us that those are the p-values. A lot of this is fluff that isn’t actually telling the reader anything new.

This experiment was aimed at demonstrating that Red and white eye colors areeye color in Drosophila melanogaster is s sex linked trait cs hence carried onin the female X-chromosome. The results matched both the expected, observed and predicted values. The experiment involved a cross-link carried between a red-eyed and white fruit fly. The values obtained were less than 1%. This means that there was no significance difference in the transmission of the red-eyed and white-eyed characteristics in the fly Drosophila melanogaster. The characteristics shown in both the F1 and F2 was due to cross link and inheritance of the traits from the parental forms. Comment by Tim I McClure: We’re going to need a bit more background in the intro portion of the abstract. For example, why do we care about model organisms? Comment by Tim I McClure: How did we get those expected ratios? Why do we care? The point of this experiment was to test whether eye color was a sex-linked trait or not, so our hypothesis was that it was sex linked, and we figured out the expected values from sex-linked heritability. So, our null hypothesis (stasticical hypothesis) was that there would be no difference between the observed and expected (from sex-linkage) phenotypic ratios. The biological interpretation of rejecting the null would be support for our hypothesis that eye color is sex-linked. Comment by Tim I McClure: What is this? Comment by Tim I McClure: What values are you talking about here? Comment by Tim I McClure: Okay, you’re talking about your p-values? If the p-values we obtained were less than 0.01 (1%), we would definitely reject our null hypothesis. This is unclear, and wrong even if it were. You will need to revisit your hypotheses in order to correctly interpret the statistical results. You also have no discussion here.

Introduction

Drosophila melanogaster is a three millimetersmall species of fruit fly which is commonly found in ripe fruits. It is mostly applied in research particular developmental biology and genetics. It is also applied in reproduction in studying the life cycle, embryonic development, understanding the complexity of living organisms and development of organs in complex organism. This is because it has homologs genes which are similar to those found in complex organisms particularly the vertebrates. It has been found that the fly grows well in the lab when feed on Blue Goo. Drosophila melanogaster has proved to be a success because it is easy to work with, has a short life cycle, one can handle large numbers of the fly, it is cheap, it is a small animal and has availability of mutant flies (class lab manual biol 105, 2016). Most importantly, it is easy to ask, answer and interpret results while working with Drosophila melanogaster. Comment by Tim I McClure: Merge these sentences, you’re basically trying to say the same thing. Comment by Tim I McClure: Good background stuff – you’ll need to cite these though. Comment by Tim I McClure: What does this tell us in terms of what we studied, especially when you aren’t telling us what blue goo is? This isn’t germane to our study at all. Comment by Tim I McClure: Always italicize, and once you’ve used a species name for the first time you abbreviate it (common models like Drosophila break that pattern, and just go by their genus name usually). Comment by Tim I McClure: Nice! Another option is your text book. Also, all of these sentences are saying basically the same thing (why Drosophila is a good model system), so try to merge these ideas accordingly. Comment by Tim I McClure: How is this different from anything else you’ve said?

In fruit flies, characteristics are inherited genetically in a similar way that resembles other complex organism. This can be shown by cross-linking the various parental forms of the fly to demonstrate the transmission of red and white-eye trait which are sex linked traits in fruit flies. This experiment was aimed at demonstrating that Red and white eye colors are sex linked traits hence carried in the female X-chromosome. The results matched both the expected, observed and predicted values. Comment by Tim I McClure: All diploid eukaryotes basically have this pattern – again, not germane to our study. Comment by Tim I McClure: Wrong tense – fix grammatical errors before submitting things! Comment by Tim I McClure: I know the lab manual kind of made it sound like sex linkage was already a “known” fact, but this is what our experiment is testing. See comments above as I’ve already covered that concept some. Comment by Tim I McClure: You need to explicitly state our hypotheses here Comment by Tim I McClure: This is interpretation!! Goes in the discussion. Comment by Tim I McClure: Huh? These ARE the results…

Hypothesis

Red and white eye colors are sex linked traits hence carried in the female X-chromosome.

Materials and methods

The procedure on lab 105 manual was followed (class lab manual biol 105, 2016). Comment by Tim I McClure: You should cite the lab manual, but only after a sentence or two describing what it is we did. We should

Results

F1 generation produced after a successful cross 1 Comment by Tim I McClure: This should all be in a table. The results section should include two tables (one for each cross), and a narrative describing the results of each section. I’d suggest setting up your table like You’re also going to need figure captions, except for tables they go above, and should describe what’s being presented in the table. This section will need substantial work.

Predicted phenotypic ratio1: 1

All off spring had red eyes

Total number of F1 flies was 100

Expected number of F1 red-eyed males was 50 against the actual 47 observed

Expected number of F1 red-eyed females was 50 against actual 57 observed

The value of red-eyed (observed-expected) ^2 / expected was 0.09

For red-eyed females, value of (observed-expected) ^2 / expected was 0.47

P-value of cross one is 73.84

P is thus less than 1 hence hypothesis is rejected

F2 generation

Predicted phenotypic ratio 25red: 25white

Total number of f2 flies was 100

Expected number of F2 red-eyed males was 25 and the actual number 98

Expected number of f2 white-eyed males is 25 against the actual 12

Expected number of red-eyed females is 50 against the actual 91

6.76 was the (observed-expected) ^2 / expected for red-eyed males

7.84 was the (observed-expected) ^2 / expected for white-eyed males

16.24 was the (observed-expected) ^2 / expected for red-eyed.

The total value for the chi-square was found to be 24.84

P-value was less than 1% hence rejected.

Cross 2: parents’ white-eyed females and red-eyed males

F2 generation

50red: 50white was the predicted phenotypic ratio.

The total number of F1 files counted was 100

The expected number of F1 white-eyed males was 50 against actual observed 36

Expected number F1 red-eyed females was 50 against 30

The value of white-eyed (observed –expected)^2 / expected was 7.84

16 was the (observed-expected)^2 / expected value for red-eyed.

The chi-squared statistics for F2 cross was 73.84

P2 value was less than 1% hence rejected.

F2 generation

The predicted phenotypic ratio of the F2 generation was 1:1

Total number of F2 flies was 100

The expected value of red-eyed males was 25 against 28

25 was the expected value of F2 white-eyed males against the actual 29 observed

The expected number of F2 red-eyed females was 25 against the actual 24 observed

25 was the expected value for F2 white-eyed females against the actual 19 observed.

The value of red-eyed males (observed –expected)^2 / expected was 0.36

0.64 was the (observed-expected)^2 / expected value for white-eyed.

The value of red-eyed females (observed –expected)^2 / expected was 0.04

1.44 was the (observed-expected)^2 / expected value for white-eyed female.

The value P2 was less than 0.5 hence rejected.

Discussion

Characteristics are genetically transmitted from parents to offspring. This is a result of each parent contributing gamete carrying the allele. For instance the red and white eyed alleles are phenotypically seen in the f1 offspring due to the offspring inheriting the characteristic via genetics and cross linkage. However, inheritance occurs by chance hence the disparity of the expected, predicted and observed values as seen in the results above. To confirm and reduce the chance effects, a chi square test is done. A value of more than 5% depicts that the value is true hence the hypothesis accepted. But a chi square value of less than 5% indicates that the hypothesis should be rejected. In this case the values obtained were less than 1% which formed the basis of rejecting our hypothesis. Therefore, there was less chances of error in stating there is a difference, when actually there was no significance difference. This means that there was no significance difference in the transmission of the red-eyed and white-eyed characteristics in the fly Drosophila melanogaster. The characteristics shown in both the F1 and F2 was due to cross link and inheritance of the traits from the parental forms (class lab manual biol 105, 2016). Comment by Tim I McClure: The first thing your discussion should be addressing is interpreting your results. Did your data support your hypothesis? Then, you should get into what that means biologially, and why it matters ( why do we care about sex linkage? Disease genetics?) Then, you can spend a few sentences talking about potential issues. Comment by Tim I McClure: You’re basically describing the hypothesis testing and that’s not the point here.

The genes for the eye color is a sex linked trait hence carried on the X-chromosome. This translate that female have two copies of these traits compared to the male. Moreover, the red trait allele is dominant over the white eyes which are phenotypically expressed only in recessive form. Comment by Tim I McClure: You already said this

Conclusion

Sex linked trait like eye color in Drosophila melanogaster are carried on the X-chromosome. Females have two copies of these traits since the X-chromosome is large and long to carry more traits. As such, the female parental forms determines the inheritance of such traits in the male generation. Comment by Tim I McClure: The fathers also determine their daughter’s genetics, if they’re dominant (which they would have received from their mothers… so diseases can jump from grandma to granddaughter, for example). Make sure to explain this whole point if you’re going to go here…it’s a good one and I think can lead into your discussion of disease genetics.

References

class lab manual biol 105. (2016). Comment by Tim I McClure: You should have a couple articles or the textbook cited here as well.