.Zygote: In humans, the male gamete is called sperm, and the female gamete is called an egg. When the gametes join they form a cell called a zygote. Human sperm and eggs contain 23 chromosomes. Human zygotes contain 46 chromosomes.
Spermatogonia: (46 chromosomes, 92 chromatids)
- Has a pair of each chromosome, and each individual chromosome has two chromatids.
- Undergoes mitosis (normal cell division) to produce a primary speratocyte.
Secondary oocyte: The secondary oocyte is the cell that is formed by meiosis I in oogenesis. Thus, it has only one of each pair of homologous chromosomes. In other words, it is haploid. However, each chromosome still has two chromatids, making a total of 46 chromatids (1N but 2C). The secondary oocyte continues the second stage of meiosis (meiosis II), and the daughter cells are one ootid and one polar body.
Secondary oocytes are the immature ovum shortly after ovulation, to fertilization, where it turns into an ootid. Thus, the time as a secondary oocyte is measured in days.
The secondary oocyte is the largest cell in the body, and in humans is just visible to the naked eye.
Oogonia: An oogonium (plural oogonia) is a small diploid cell which upon maturation forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes. Oogonia are the cells that turn into primary oocytes in oogenesis. They are diploid, i.e. containing pairs of homologous chromosomes. There are 23 chromosome pairs. Thus, there are 46 chromosomes