The zygote inherits two fully active X chromosomes and begins re-inactivation of the paternal X chromosome (XP) at the 4- to 8-cell stage. In the trophectoderm (extra-embryonic cells, shown in ...

Each human has 46 chromosomes, 22 pairs of autosomes and 1 pair of sex ... each parent contributes 23 chromosomes to the zygote through a process of chromosomal reduction called meiosis (Fig ...

So, nuclear genes come in allelic pairs that are often subtly different ... b and c from the male parent). The zygote that results from fertilization inherits one nuclear allele of each gene ...