CP Biology – Inheritance Practice Test

Genetic variation among siblings arises because each child receives a unique mix of chromosomes and gene variants from the parents. In sexual reproduction, each parent has two copies of every gene, but gametes carry only one copy. During meiosis, crossing over creates new combinations of alleles, and independent assortment shuffles which chromosome from each parent ends up in a gamete. When a sperm fertilizes an egg, the zygote ends up with a specific, unique combination of maternal and paternal alleles. With many genes involved, these differences across genes lead to different traits and appearances among siblings. Environmental factors can also influence how traits are expressed, adding even more variation. The other ideas don’t fit because siblings do not inherit identical genetic material (that would be true for identical twins, not typical siblings), they do not necessarily have the same phenotype, and they are not from different species.