Question

5. Humans with autosomal trisomy sometimes survive past birth, but humans with autosomal monosomy do not, because: a) monosomy reveals recessive lethal alleles whereas trisomy does not b) monosomy disrupts the proper balance of gene products produced from genes on different chromosomes, whereas trisomy does not c) for certain chromosomes, it is possible to “turn off” a third copy to avoid too much gene expression d) this is a trick question because some people with autosomal monosomy survive

Answer 1

The fact that autosomal monosomy is more harmful to humans than are autosomal trisomy. The rationale behind this is that autosomal monosomy reveals recessive lethal alleles whereas trisomy does not. The lethal recessive alleles do not show effects unless under certain conditions that allow their expression. A mutation in the normal allele may aggravate the effects of the recessive lethal alleles.

Thus, option (a) is correct.