Activity 7: Boy or Girl? Directions: Complete the Punnett square below and answer the guide questions. XY sperm weds X Y mother XX X X Cate Guide Questions: 1. What will be the sex of the child produced when an egg is fertilized by a sperr that has a Y chromosome? 2. What sperm must fertilize an egg to result a female child? 3. How many percent will they have a male offspring? 4. Which chromosomes determine a person's sex or gender?