If requested by the appointing authority and approved by the Department layoff of employees in any one of the following categories may be made before layoff of employees in the other categories: intermittent, part-time, full-time; provided that full-time employees laid off as a result of the application of this section may elect transfer to remaining intermittent and part-time positions in accordance with the provisions of chapter 7. of the Act governing demotion in lieu of layoff.