Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: This sperm is ready to penetrate the membrane of this egg. Notice the difference in size of the sperm and egg. Why is the egg so much larger? The egg contributes all the cytoplasm and organelles to the zygote. The sperm only contributes one set of chromosomes. Answer: sperm
Which part of the reproductive process only contributes one set of chromosomes?