Case 3 - SMA carrier risk - results

Calculation methods

Two approaches to tackling this problem are illustrated on this website.

• Firstly, by construction of gamete square

• Secondly, by analysis of mating types and segregation patterns

In addition, calculations are shown using either approximate allele frequencies (ignoring point mutations, and rounding allele frequencies to the nearest whole percentage), or allele frequencies are used as described in the reference: Ogino et al, Eu J Hum Genet, 2004, Dec 12 (12) 1015-23.

Rounded allele frequencies:

0 - copy disease allele = 0.01

1 - copy disease allele = 0.00

1 - copy normal allele = 0.95

2 - copy normal allele = 0.04

Unrounded allele frequencies:

0 - copy disease allele = 0.013

1 - copy disease allele = 0.00024

1 - copy normal allele = 0.95

2 - copy normal allele = 0.038