TITLE : Drosophila melanogaster OBJECTIVE : i. To calculate the offspring characteristics that given same to the Mendel’s law of inheritance. ii. To make students creative to do the experimental design the crosses of flies. INTRODUCTION: Drosophila melanogaster is a small, common fly found near unripe and rotted fruit. It has been in use for over a century to study genetics and lends itself well to behavioral studies. Thomas Hunt Morgan was the preeminent biologist studying Drosophila early in the 1900's. Morgan was the first to discover sex-linkage and genetic recombination, which placed the small fly in the forefront of genetic research. Due to it's small size, ease of culture and short generation time, geneticists have been using Drosophila ever since. It is one of the few organisms whose entire genome is known and many genes have been identified. Fruit flies are easily obtained from the wild and most biological science companies carry a variety of different mutations. In addition these companies sell any equipment needed to culture the flies. Costs are relatively low and 1
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TITLE : Drosophila melanogaster
OBJECTIVE :
i. To calculate the offspring characteristics that given same to the Mendel’s law of
inheritance.
ii. To make students creative to do the experimental design the crosses of flies.
INTRODUCTION:
Drosophila melanogaster is a small, common fly found near unripe and rotted fruit. It has
been in use for over a century to study genetics and lends itself well to behavioral studies.
Thomas Hunt Morgan was the preeminent biologist studying Drosophila early in the
1900's. Morgan was the first to discover sex-linkage and genetic recombination, which
placed the small fly in the forefront of genetic research. Due to it's small size, ease of
culture and short generation time, geneticists have been using Drosophila ever since. It is
one of the few organisms whose entire genome is known and many genes have been
identified.
Fruit flies are easily obtained from the wild and most biological science companies carry
a variety of different mutations. In addition these companies sell any equipment needed
to culture the flies. Costs are relatively low and most equipment can be used year after
year. There are a variety of laboratory exercises one could purchase, although the
necessity to do so is questionable.
PROCEDURE:
There are a few methods in fainting the flies. In this practical, we are given chloroform of
anesthetization kit for fainting the flies. The lab assistants show to us the technique. The
newly fainted flies should be examined immediately. Always ready with cotton or cotton
buds with the anesthetizer before hands as to avoid the sudden awaken of the flies.
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Part I
i. Firstly we identify the wild type and mutant flies. We had examined their
morphology thoroughly before we do the crosses. We use the dissecting
microscope in lab to examine the flies.
ii. We had design our experiment properly in order to yield expected results.
iii. We choose the traits that can breed through based on autosomal and sex-linked.
iv. Before we hands the flies, we show our experimental design to our Tutor for
approval. Then we inform the lab assistant the flies that we want to use.
Part II
i. We have chosen five pairs of traits that follow: Mendel Law 1, Mendel Law 2 and
X-linked.
ii. We had bred the homozygote parents of wild type and homozygote mutant.
iii. When we see the larvas have emerged from the medium, we took out the parents
and kill them immediately. The Tutor and lab assistants had shown us how to kill
the flies. We also make sure that no one of flies flying in the lab.
iv. We let the larvas grow. We placed the virgin females in new tubes with their male
siblings. When we see another generation of larvas (F2) emerge, we killed the F1.
v. Every day we go to lab to see if we get the F2 generation or not. If we have that
flies, we anesthetize the adult F2 and we count.
vi. We had analysed the results using Chi-square.
Parents generation
Mendel Law 1 Vestigial Wing x Wild Type
Mendel Law 1 Ebony x Wild Type
Mendel Law 2 Sephia, Ebony x Wild Type
X-linked White Eye (M) x Wild Type (F)
X-linked Wild Type (M) x White Eye (F)
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RESULT & DISCUSSION:
Mendel Law 1
Law 1 : Vestigial Wing x Wild Type
Legend : S- Dominant allele control the wild type wing trait
s- Recessive allele control the vestigial wing trait
Cross : VV x vv
Result (f2 generation): 3:1
Characteristic O (observation
values)
E (Expected values) (O-E)2
Vestigial 21 1/4 x 130 = 32 121
Wild Type 109 ¾ x 130 = 98 121
CHI-SQUARE TEST:
Degrees of freedom = 2-1
= 1
X2 = ∑ (O-E)2 / E
Where,
O = Observed data in each category
E = Observed data in each category based on the experimenter’s hypothesis
S = Sum of the calculation for each category
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X2 = ∑ (21-32)2/ 33 + (109-98)2/ 98
= 4.9
= 1%< X2 <5%
= 0.01< X2 < 0.05
Discussion:
From the result, the observation value is 21 for vestigial wing and 109 for wild type wing.
So, wild type is dominant to vestigial wing. Based on the observations, the hypothesis is
‘Wild type (V) is dominant to the Vestigial (v).
From the chi-square test, the chi-square value is lower than 0.05. So, that means the null
hypothesis is rejected for the experiment. From the chi-square test the data and
hypothesis do not have a good fit.
During the experiment, the data are collected not accurately due to the lost of the
Drosophila melanogaster during the researcher change the place of the Drosophila
melanogaster and the another factor is due to the fatal problem.
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Mendel Law 1
Legend:E- Dominant allele for wild typee- Recessive allele for ebony body
Parent : Ebony x Wild type ee EE
G1 :
F1 : All wild typeEe
F1xF1 : 5 wild type x 5 Wild type Ee Ee
G2 :
F2 :
Chi square test: x2 = ∑(O-E)2/ E
Drosophilla types Observed data (O) Experiments’ hypothesis (E)
(O-E)2/ E
Wild type 119 ¾ x 157 = 117.75 (119-117.75) / 117.75 = 0.013