Genes of fruit fly practical write up

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2 DATA COLLECTION and PROCESSING

Part A

2.1        Raw Data: Drosophila Fruit Fly’s

        Colour of Body

The crosses in this simulation were all run against the wild type. i.e. every cross was made between the wild type Drosophila fly and another colour of fly

Black Coloured Body

Table 2.1.1

Above is the raw data table showing the drosophila fly’s colour when wild type (colour) and a black colour are crossed. This cross is F2 and so shows which gene is recessive and which is dominant. The F1 crosses are not shown as when a dominant gene wild body coloured fly and a recessive black body coloured fly are crossed all the offspring have wild type genes. As can be seen from the data there is a 3:1 ratio of Wild type coloured body’s to black coloured bodies.  Obviously the Wild type is the dominant and the Black body is the recessive. There were roughly the same number of male and females for each colour suggesting that the cross was not sex related.

Yellow Coloured Body

Table 2.1.2

The raw data for the yellow coloured body and the wild type coloured body is the same in that it has the same 3:1 ratio for the dominant wild type body to the recessive yellow body. This cross is different however in that after the cross was made there were no yellow females. This could be because of a degenerate disease that only affects females who have double of a particular trait

Ebony Coloured Body

Table 2.1.3

Ebony coloured body and Wild type coloured body are much the same as Black coloured body and the Wild type body. This is because they both aren’t sex related and they had very similar numbers for both male and female wild and black colour. In both crosses Wild type colour was dominant and ebony and black recessive, as when the wild type body colour has been added together there is roughly three times as many as there are ebony coloured body flies.

Sable Coloured Body

Table 2.1.4

Sable coloured body, Tan Coloured body and Yellow coloured body are all also very similar. They are all sex dependant, in that in each cross there was no female for the recessive trait. i.e. there was no female sable body coloured fly. This could be due to a disease that only affects the flies which have double of that trait i.e. females XX. As also can be seen the ratio is 3:1 where the Wild type is dominant and the sable coloured body is recessive.

Tan Coloured Body

Table 2.1.5

Tan body colour being one of the three crosses that were sex dependant is also very similar to yellow and sable body colour. There were no females for the recessive tan coloured body. This could also be due to a disease that affects females of the recessive trait. The ratio is 3:1 as the wild type is dominant and the tan coloured body recessive.

2.2         Processed Data

        Colour of Body

Wild type body and Yellow body

Table 2.2.1

Table 2.2.2

Chi-squared test statistic: 0.4233

The punnet squares above show that the F1 generation of flies is always totally the dominant gene which in this case is the wild type body colour. The F2 generation Flies is according to Mendel’s Law of Segregation going to be roughly in a ratio of 3:1 where in this case there are 3 wild type body coloured flies to every 1 yellow body coloured fly. The Table above shows the full results of the fly crossing simulation. As can be seen they are roughly in a ratio of 3:1 which was the hypothesis tested. The hypothesis tested had a very small chi squared value which means that the distribution of the data is small correlating to an accurate simulation. The chi squared value does not prove the data to be exactly correct it just suggests that it is likely to be true. The “expected” value is the number of flies expected to be each genotype group. It is usually 3:1 as this is the ratio that Mendel said that each genotype when crossed would turn out as. There were no Female yellow body coloured flies in this cross. This suggest that is could be due to a disease or something similar that only affects the flies that have double of a particular gene e.g. females as they have XX chromosomes. The Chi Squared value is well above 0.05 and so this suggests that the hypothesis tested is true. The level of significance is also another tool used to help suggest the hypothesis used to be more than likely. The level of significance concerning  this yellow body fly colour is just over half at 0.5153 this is the minimum value that the level of significance can be while still supporting the hypothesis. This is because when the level of significance is multiplied by 100 it gives the percentage probability of the hypothesis actually happening.

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Wild type body and Black body

Table 2.2.3

Table 2.2.4

Chi-squared test statistic: 0.972

The punnet square of the black body also show the norm as both F1 and F2 match up in ratios with all the other crosses. Black coloured body and Ebony coloured body are the only two coloured body crosses that aren’t affect by sex. i.e. a particular gender doesn’t drop out that has a particular set of genes. This is probably due to the fact that this cross is more stable in that it doesn’t have any diseases associated with it. This means that ...

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