Thalassemia is blood disorder where individuals with thalassemia produce too muc
ID: 272064 • Letter: T
Question
Thalassemia is blood disorder where individuals with thalassemia produce too much iron. This disease is inherited as an autosomal recessive. It has been hypothesized that heterozygous individuals have some immunity to malaria (similar to sickle cell anaemia). You obtain blood samples from a Mediterranean population of humans where malaria is endemic and among 100 individuals find 3 with thalassemia and 50 who are carriers. Are these results consistent with the hypothesis that heterozygous individuals have partial immunity to malaria?
Explanation / Answer
The steps involved here,
Step : 1: Calculation of the allele frequencies:
Phenotype
Genotype
Freequency
Allele T
Allele t
Total
Normal
TT
47
94
0
94
Carriers
Tt
50
50
50
100
Thalassemia
tt
3
0
6
6
Total
Total
100
144
56
200
Allele T
= 144/200
= 0.72
Allele t
= 56/200
= 0.28
Step: 2: Calculation of the expected genotype frequencies
Normal
TT
= 0.72*0.72= 0.518
*100= 52
Carriers
Tt
= 2*0.72*0.28= 0.403
*100= 40
Thalassemia
tt
= 0.28*0.28= 0.078
*100= 8
Step: 3: Comparison of observed and expected genotype frequencies statistically:
Null hypothesis: The observed values are not deviating from the expected values.
Test Static- Chisquar test:
Category
TT
Tt
tt
Observed values
47
50
3
Exprected Values
52
40
8
Deviation
-5
10
-5
D^2
23.4256
93.7024
23.4256
D^2/E
0.45
2.32
2.99
5.76
X^2
5.76
Degrees of freedom
1
Inference: As the calculated chi-square value i.e. 5.76 is greater than the table value i.e. 3.84 at 1DF and 0.05 probability, hence the null hypothesis is rejected. Which means ,these results are not consistent with the hypothesis that heterozygous individuals have partial immunity to malaria.
If there is any raw data of malaria immunity, then we need follow another approach, so, do verify your data and let me know.
Phenotype
Genotype
Freequency
Allele T
Allele t
Total
Normal
TT
47
94
0
94
Carriers
Tt
50
50
50
100
Thalassemia
tt
3
0
6
6
Total
Total
100
144
56
200
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