β globin gene mutations in patients with β thalassaemia major from the eastern region of Saudi Arabia
| Mutation | Type of mutation | Nucleotide change | Type of thalassaemia | Independent alleles | Origin of mutation | Original reference | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Number | Frequency | ||||||||||||
| CD39(C→T) | Nonsense | Substitution C→T | β° thalassaemia | 17 | 32.1% | Mediterranean, European | 6 | ||||||
| IVS-1 3' end-25bp | Splice junction frameshift | Deletion of 25 bp | β° thalassaemia | 12 | 22.6% | Asian, Indian | 7 | ||||||
| −2CD8(−AA) | Frameshift | Deletion of 2A | β° thalassaemia | 8 | 15.1% | Turkish | 8 | ||||||
| IVS-2+1(G→A) | Splice junction change | Substitution G→A | β° thalassaemia | 8 | 15.1% | Mediterranean, Tunisian, African-American | 9 | ||||||
| −1CD44(−C) | Frameshift | Deletion of C | β° thalassaemia | 4 | 7.5% | Kurdish | 10 | ||||||
| +1CD8/9(+G) | Frameshift | Insertion of G | β° thalassaemia | 2 | 3.8% | Asian, Indian | 11 | ||||||
| IVS-1+5(G→C) | Consensus change | Substitution G→C | β+ thalassaemia | 1 | 1.9% | Indian, Chinese, Melanesian | 11 | ||||||
| IVS-1+5(G→T) | Consensus change | Substitution G→T | β+thalassaemia | 1 | 1.9% | Mediterranean, Blacks | 12 | ||||||
Calculation of allele frequency:
There are 31 patients with β thalassaemia major.
No of alleles = 31×2 = 62 alleles.
There are 4 pairs of sibs; hence 62−8 = 54 alleles.
Subtract 1 allele for first cousin = 53 independent alleles.
Detection rate = 53/53×100 = 100%.