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Principles of Genetics

ANGLIA RUSKIN UNIVERSITY

DEPARTMENT OF LIFE SCIENCES
Principles of Genetics MOD002804

Assessment 2

Part A: Questions from the Drosophila melanogaster cross practical
1) Present the results of the Drosophila cross in a suitable format. Include your results and class results. (5)
2) Explain why a reciprocal cross might be carried out in an experiment like this. (4)
3) Research the genetic basis of vestigial wings in Drosophila melanogaster. (2)
4) Carry out a Chi square test of the class results based on what you found out about the genetics. Write a null hypothesis and show all of the steps clearly. State whether you should accept or reject the null hypothesis and state your conclusion. (10)

Part B: Questions from the polytene chromosomes practical
1) From your own observations in the practical, estimate the width of a polytene chromosome on your slide. (2)
2) What are polytene chromosomes and why do they arise? (10)
3) Research other species and tissues where polytene chromosomes have been found. (10)
4) Discuss the nature of "puffs" that occur in polytene chromosomes during development. (10)

Part C: Questions from the bacterial transformation practical
1) How much DNA in ng was added to each tube of bacteria? If 250pg of DNA was required, how many l would have been needed? Show your workings clearly. (6)
2) In week 1 of the practical, plasmids were introduced into competent bacteria and plated onto selective media. Present the results of your findings in an appropriate way and state which plasmid contains which resistance gene? (10)
3) Calculate the transformation efficiency for each of the transformations you performed. Show your workings clearly. (5)

Transformation efficiency (transformants/g) = Number of colonies on plate
g of DNA per transformation

5l of plasmid at 2ng/l were used per transformation.

4) What factors may affect transformation efficiency and why? (8)
5) Present results of the gel electrophoresis including labels for each lane. (6)
6) Give an estimate for the sizes of the plasmids in base pairs. (2)

Please do not exceed the word count of 1000 words. This word count does not include titles, tables, legends, figures or references.

A further 10 marks are available for references, presentation, clarity, depth of understanding and scientific content.

This assessment is due in Thursday 5th December 5pm.

Helen McRobie 2013

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Solution Preview

This response can also be found duplicated in the attached file. Some links and formats may not come through correctly, but they can be found in the attached document. Read through the answer provided and try and put what is written into your own words as much as possible. Pay attention to word limits and formats. Be sure to use italics for latin names. As well, you should consult previous assignments and lab reports to gauge how your instructor prefers references, figures and tables to be formatted. Each instructor is different and they ultimately will mark you based on their preference. These formatting options are what are often called "easy marks" Easy for the instructor to deduct and easy for you the student to do correctly and not lose precious points.

Part A: Questions from the Drosophila melanogaster cross practical
1) Present the results of the Drosophila cross in a suitable format. Include your results and class results. (5)
2) Explain why a reciprocal cross might be carried out in an experiment like this. (4)
3) Research the genetic basis of vestigial wings in Drosophila melanogaster. (2)
4) Carry out a Chi square test of the class results based on what you found out about the genetics. Write a null hypothesis and show all of the steps clearly. State whether you should accept or reject the null hypothesis and state your conclusion. (10)

Drosophila melanogaster is often used as model organism for investigating genetics. The development of practically the entire theory of chromosomal inheritance is based on research using Drosophila. For further reading, I highly recommend the following text: Ashburner M, Thompson JN (1978). "The laboratory culture of Drosophila". In Ashburner M, Wright TRF. The genetics and biology of Drosophila 2A. Academic Press. 1-81

1. This question wants you to present your results in a suitable format. As one of the constraints to your assignment is a 1000 page word limit that does not include figures, graphs and tables you should present your answers as such. You have provided the class results, but you will need to present your raw data as well. Something like the following table:

Results for the F2 generation of the Drosophila melanogaster cross
Individual Class (includes individual results)
Normal winged Male 592
Female 692
Total 1284
Vestigial winged Male 162
Female 120
Total 282

Also, depending on your instructor's preference, this table should have a title. Something like: Table 1. Analysis of the F2 generation of normal and vestigial winged Drosophila melanogaster. The table title goes either above or below the table. This depends on your instructor's preference. It is a good idea to look back on previous assignments or lab reports to see.

One more thing: always be sure to italicise Drosophila melanogaster. That is an area that instructors love to deduct points from.

2. First, you should start by defining what a reciprocal cross is. Use the definition given in your class. Alternatively use this definition: A reciprocal cross is a cross between different strains with the sexes reversed. For example: female A x male b AND male A x female B are reciprocal crosses.
Then answer the question by writing out something like this: In an experiment like this, a reciprocal cross is carried out to test the role of gender on a given inheritance pattern. Via principles of dominant and recessive alleles, one can make an inference as to which sex ...

Solution Summary

This question is three parts concerning some common principles of genetics. The first part deals with a cross of normal to vestigial winged fruit flies. The questions explore common principles involved in this type of cross.

The second part looks at polytene chromosomes. The original question did not provide any raw data, so the answer provides guidance on how to solve the question.

The third part looks at bacterial transformation. Again, the original question does not provide the raw data showing the results of the plating experiment and the gel electrophoresis. The solution does provide help on how to answer the question.

For each part, references are provided along with guidance and tips on how best to respond to this question (and questions of a similar nature). Links are also provided to helpful websites and further reading.

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