We have analysed the possibility of scaling the sexual Penna ageing model. Assuming that the number of genes expressed before the reproduction age grows linearly with the genome size and that the mutation rate per genome and generation is constant, we have found that the fraction of defective genes expressed before the minimum reproduction age drops with the genome size, while the number of defective genes eliminated by the genetic death grows with genome size. Thus, the evolutionary costs decrease with enlarging the genome. After rescaling the time scale according to the mutational clock, age distributions of populations do not depend on the genome size. Nevertheless, enlarging the genome increases the reproduction potential of populations.