UNIT 11 ASSIGNMENT C
Monohybrid inheritance investigation
Null hypothesis: there is no significant difference between the observed ratios for eye colour of fruit
flies and their expected ratio
Alternative hypothesis: there is a significant difference between the observed ratio for eye colour of
fruit flies and their expected ratio
observed results from stimulation: out of 86 fruit flies, 45 flies are male and their eye colour are white
(white eyed) and 41 of the remaining flies are female flies eye colour are wild type (red-eyed)
genetic cross of parents
parental phenotypes: white eyed female X red-eyed male
parental genotypes: XWXW X XW+Y
, gametes: XW, XW X XW+, Y
punnet square:
xw Xw
Xw+ Xw+xw Xw+xw
y xw Y xwY
F1 genotypes: 50% Xw+Xw (heterozygous) and 50% XwY (homozygous recessive)
F1 phenotypes 50% red eyed females and 50% white eyed males
Expected ratio from genetic cross: 1:1
Chi squared test
phenotype Observed(o) Expected (E) O-E (O-E)2 (O-E)2/E
Red eyed 41 43 -2 4 0.093
female
White eyed 45 43 2 4 0.093
male
X2 = 0.186
Conclusion and explanation
The chi squared value is 0.186 and is smaller than the critical value which is 3.84 at the 5% level of
significance and 1 degree of freedom. Therefore, the null hypothesis is accepted because the difference
between the observed and expected is ratios of fruit flies for eye colour is insignificant therefore there
is greater than 5% probability that the results are due to chance.
One possibility that may cause small insignificant differences in my results is some fertilised cells may
not survive to grow into adulthood, a biologist called Thomas hunt Morgan conducted many
experiments on fruit flies and on thing he was wanted to find out was why female flies never had white
eyes and one possibility he came up with is that they may have died early in development. Small
Sample size may also be why the results are insignificant, as a larger sample gives a more reliable
results with greater precision so therefore a smaller sample size affects the reliability of the results and
increases the chance of errors occurring. The inheritance pattern observed is similar to what is
expected, following Mendel’s law of inheritance. Insignificant differences may be due to recombination
in rare crossing over event. Individuals have two alleles, according to Mendel's Law of Segregation,
and a parent transfers only one allele to his or her offspring. According to the Law of Dominance,
dominant alleles often mask recessive alleles. When a cross is made between any two opposing
characters, the dominant character is always expressed. When the alleles Xw+ and Xw cross ( Xw+Xw),
Monohybrid inheritance investigation
Null hypothesis: there is no significant difference between the observed ratios for eye colour of fruit
flies and their expected ratio
Alternative hypothesis: there is a significant difference between the observed ratio for eye colour of
fruit flies and their expected ratio
observed results from stimulation: out of 86 fruit flies, 45 flies are male and their eye colour are white
(white eyed) and 41 of the remaining flies are female flies eye colour are wild type (red-eyed)
genetic cross of parents
parental phenotypes: white eyed female X red-eyed male
parental genotypes: XWXW X XW+Y
, gametes: XW, XW X XW+, Y
punnet square:
xw Xw
Xw+ Xw+xw Xw+xw
y xw Y xwY
F1 genotypes: 50% Xw+Xw (heterozygous) and 50% XwY (homozygous recessive)
F1 phenotypes 50% red eyed females and 50% white eyed males
Expected ratio from genetic cross: 1:1
Chi squared test
phenotype Observed(o) Expected (E) O-E (O-E)2 (O-E)2/E
Red eyed 41 43 -2 4 0.093
female
White eyed 45 43 2 4 0.093
male
X2 = 0.186
Conclusion and explanation
The chi squared value is 0.186 and is smaller than the critical value which is 3.84 at the 5% level of
significance and 1 degree of freedom. Therefore, the null hypothesis is accepted because the difference
between the observed and expected is ratios of fruit flies for eye colour is insignificant therefore there
is greater than 5% probability that the results are due to chance.
One possibility that may cause small insignificant differences in my results is some fertilised cells may
not survive to grow into adulthood, a biologist called Thomas hunt Morgan conducted many
experiments on fruit flies and on thing he was wanted to find out was why female flies never had white
eyes and one possibility he came up with is that they may have died early in development. Small
Sample size may also be why the results are insignificant, as a larger sample gives a more reliable
results with greater precision so therefore a smaller sample size affects the reliability of the results and
increases the chance of errors occurring. The inheritance pattern observed is similar to what is
expected, following Mendel’s law of inheritance. Insignificant differences may be due to recombination
in rare crossing over event. Individuals have two alleles, according to Mendel's Law of Segregation,
and a parent transfers only one allele to his or her offspring. According to the Law of Dominance,
dominant alleles often mask recessive alleles. When a cross is made between any two opposing
characters, the dominant character is always expressed. When the alleles Xw+ and Xw cross ( Xw+Xw),
