Below are three statements. Classify them as examples of independent orientation, crossing over, or random fertilization.

I: The formation of a zygote from an egg and a sperm is an unpredictable event.
II: Random combinations of paternal and maternal chromosomes end up in gametes.
III: An allele on the paternal chromosome 18 ends up on the maternal chromosome 18.

A) I: random fertilization; II: random fertilization; III: independent orientation
B) I: random fertilization; II: crossing over; III: independent orientation
C) I: independent orientation; II: random fertilization; III: crossing over
D) I: random fertilization; II: independent orientation; III: crossing over

Meiosis produces male and female gametes with genetic variations. Each of the male gametes has equal chances to fertilize female gamete with any gene combination. Since the presence of specific gene sequences does not affect the probability of fusion of male and female gametes, fertilization is said to be a random event.

Each of the homologous pair of chromosome aligns itself independently of the other pairs on cells' equator during metaphase I. This independent orientation of homologous pairs during metaphase I lead to independent segregation of paternal and maternal chromosomes of each homologous pair during anaphase I. So, gametes with various combinations of paternal and maternal chromosomes are formed.

Exchange of genetic material between non-sister chromatids of homologous pair 18 represents crossing over. It leads to shuffling of an allele from the paternal chromosome 18 to the maternal chromosome 18.