= Solution
Let $A_i(s)$ be age in years at follow-up time $s$ and let $G_i\in\{0,1\}$ indicate the genetic risk factor. An age-dependent <log-linear transition intensity model> is
$$
\boxed{q_{12,i}(s)=\exp\{\theta_0+\theta_A(A_i(s)-50)+\theta_GG_i\}.}
$$
Here $e^{\theta_0}$ is the onset <baseline hazard> for a 50-year-old without the factor; $e^{\theta_G}$ is the genetic <hazard ratio>, and $e^{\theta_A}$ is the <hazard ratio> per additional year of age. A smooth function of age could replace the linear age term if a constant age <hazard ratio> were unsuitable.
Under the stated constant multiplicative <hazard ratios>, the requested extrapolation is therefore \b[the baseline rate times both multipliers]:
$$
\boxed{q_{12}(60,1)=q\,\alpha_1\alpha_2^{10}.}
$$
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