Answer:
20 chromosomes in sperm cells and 40 chromosomes in zygote.
Explanation:
Mouse is a diploid organism, having two sets of chromosomes. Each somatic cell of mouse has 40 chromosomes (20 pairs of chromosomes). Gametes (eggs or sperm) are produced by the process of meiosis that leads to formation of daughter cells with half number of chromosomes as present in parent cell.
Hence, each mouse sperm or egg will carry 20 chromosomes. Zygote is developed by fusion of male gamete (sperm) and female gamete (egg). Hence, the number of chromosomes in mouse zygote will be 40.
