Practical Report: Drosophila BreedingAim In this practical experiment I will cross wild fruit flies with vestigal fruit flies, to investigate which one is dominant or recessive and their characteristics

Hani Ali Page of

BTEC ND1

Practical Report: Drosophila Breeding

Aim

In this practical experiment I will cross wild fruit flies with vestigal fruit flies, to investigate which one is dominant or recessive and their characteristics

Introduction

Drosophila melanogaster (fruit fly) is a common, generally innocuous insect that feeds on the fungi growing on fruit.

They are productive breeders, a single mating and they produce a hundreds of offspring and new generation can be bred every two weeks.

These characteristics make the fruit fly convenient organism for genetic studies and the fact that they have only four pairs of chromosomes, which are easily distinguishable with a light microscope. They have 3 pairs of autosome and one pair of sex chromosomes.

Female drosophila has a homologous pair of X chromosomes, and males have one X chromosome and one Y chromosome.

An embryologist named Thomas hunt Morgan, was the first to associate a specific gene with a specific chromosome, for his work he selected species of drosophila (fruit fly). Morgan spent a year breeding the flies and looking for variant individuals. Morgan discovered a single male fly with white eyes instead of usual red eye. He mated the white-eyed male fly with a red-eyed female fly and all F1 offspring had red eyes, suggesting that red-eyed fly was dominant.

Morgan bred female + male from F1 offspring. He observe 3:1 phenotype ratio among the F2 offspring, however Morgan also realised that white-eyed trait showed up only in males, all F2 females had red eyes, while half the males had red eyes and half had white eyes. Somehow, a fly’s eye colour was linked to its sex.

Morgan deduced that the gene effected the white-eyed mutant is located exclusively on chromosome. There is no corresponding eye-colour locus on the Y chromosome, so females XX carry only one, because the mutant allele is recessive, a female will have white-eyes only if she receives that allele on both X chromosomes. For male on the hand, a single copy of mutant allele counters white-eyes, since a male has one X chromosome, there can be no wild type allele present to offset the recessive allele.

Farmers used the technique of crossing over for centuries, in order to get the best yeasts, crops e.t.c, but Mendel was the first person who did real genetic study in scientific way

Apparatus

Culture medium
Growth medium
Plastic tube with sponge bung,
Small plastic ladder
Yeast
Water
Piece of paper/towel
Microscope
Black wand
Flynap

Method

Pour 2mm of growth medium into plastic container.
Add 10ml of water to dampen the medium
The medium will turn blue and then add 1 pinch of yeast by sprinkling it on the top.

Practical Report: Drosophila BreedingAim In this practical experiment I will cross wild fruit flies with vestigal fruit flies, to investigate which one is dominant or recessive and their characteristics

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