The fruit fly Drosophila melanogaster as a source of much of the chromosome theory of heredity.

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The fruit fly Drosophila melanogaster as a source of much of the chromosome theory of heredity.

ABSTRACT

This investigation centres upon the fruit fly Drosophila melanogaster as a source of much of the chromosome theory of heredity. The Drosophila was chosen due to its ease of cultivation within the laboratory as well as the many previous studies performed on it from which information could be drawn.

The hypotheses under investigation are:

Ho: The inheritance of both wing length and eye colour are not sex-linked.

Hi: The inheritance of both wing length and eye colour are sex linked.

This was tested by initially crossing three vestigial winged, red-eyed males with four normal winged, white-eyed females. The F1 generation were then allowed to interbreed after their number and phenotypes had been recorded. The F1 generation interbreeding cross consisted of three normal winged, white-eyed males being crossed with four normal winged, red eyes females. The F2 generation produced were then counted and their number and phenotypes were recorded (i.e. how many normal wing, red eye females produced etc) this cross concentrated upon investigating the inheritance of wing length, while a reciprocal cross was set up to investigate the inheritance of eye colour. The reciprocal cross was three normal winged, white-eyed males and four vestigial winged, red-eyed females. Again the F1 generation were allowed to interbreed after phenotypes and numbers were recorded. The F1 cross was three vestigial winged, red-eyed males and four normal winged white-eyed females. The F2 generation were then counted and phenotypes recorded as done previously.

The hypotheses would be tested by comparing the actual results obtained with the expected ones, if a 3:1 dominant: recessive characteristic ratio was obtained in the F2 generation implying sex-linkage had occurred. If there was an agreement between expected and actual results this would confirm a 3:1 ratio and that the hypotheses were shown to be correct and wing length and eye colour shown to be inherited through sex linkage. The recessive traits were also shown more frequently in males than females hence again implying that the inheritance of wing length and eye colour is sex linked.

INTRODUCTION

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In the study of the genetics and in particular the study of inheritance the chosen organism experiments are based upon the fruit/ vinegar fly, Drosophila melanogaster. It is widely used due to its ease of cultivation within the laboratory as well as single pair being able to provide several hundred offspring within a space of two/three weeks. These offspring can also be observed at any stages of the life cycle and are inexpensive and readily available for genetic studies such as this.

Drosophila has been used widely in genetics for many years and has aided its development greatly. The U.S ...

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