Reproduction (1 of 6) Egg, sperm, and zygote
Eggs and sperm carry only half the usual number of chromosomes — just 23 unpaired chromosomes, carrying one version of each gene. When the egg and sperm get together, the baby receives the normal 23 matched pairs.
Reproduction (2 of 6) Chromosome duplication
When eggs and sperm are produced, the parent cell first copies each chromosome, leaving the duplicate pairs attached to one another.
Reproduction (6 of 6) Zygote with recombinant genes
When egg and sperm meet, the baby inherits a combination of genes that is totally unique: it carries versions of genes from all 4 grandparents plus any mutations that occurred when the mother and father were making the egg and sperm.