Do you mean mitosis here? Meiosis does again occur after fertilization, albeit 10-12 years after.

Yes, I should have said that after fertilization, mitosis occurs - or rather, mainly mitosis.

One reason for the confusion is that in the first two days after fertilization, the egg goes through some processes that were considered phases of Meiosis II back in ye olden days when I learned about biology and had kids. It used to be frequently said that fertilization triggers "completion of meiosis" for ovum, and that the earliest cell division that occurs in the first 48 hours take place in a phase called "the transition from meiosis to mitosis." A lot of teaching materials and texts still in use today employ this sort of language, such as these two from 1998 from 2000 respectively:

Fertilization triggers continuation of meiosis II. The ovulated oocyte is maintained at metaphase II nuclear status by increased maturation promoting factor (MPF) activity (A). Fertilization triggers continuation of meiosis II, resulting in a two-pronuclear pre-embryo displaying two polar bodies and pronucleus (B). The proposed molecular mechanisms are shown at the bottom: the fertilizing spermatozoon induces oscillations in the intra-oocyte concentrations of Ca 2. This results in proteolytic degradation of c-mos and cyclin-B, and thus discontinuation of MPF activity, which allows the pre-embryo to leave meiosis and resume regular cell divisions.

https://www.researchgate.net/figure/Fertilization-triggers-continuation-of-meiosis-II-The-ovulated-oocyte-is-maintained-at_fig5_13553203

Not only does fertilization lead to the mixing of paternal and maternal chromosomes, but it also induces a number of changes in the egg cytoplasm that are critical for further development. These alterations activate the egg, leading to the completion of oocyte meiosis and initiation of the mitotic cell cycles of the early embryo.

The increase in cytosolic Ca2+ following fertilization also signals the completion of meiosis (Figure 14.42). In eggs arrested at metaphase II, the metaphase to anaphase transition is triggered by a Ca2+-dependent activation of the anaphase-promoting complex. The resultant inactivation of MPF leads to completion of the second meiotic division, with asymmetric cytokinesis (as in meiosis I) giving rise to a second small polar body.

Following completion of oocyte meiosis, the fertilized egg (now called a zygote) contains two haploid nuclei (called pronuclei), one derived from each parent. In mammals, the two pronuclei then enter S phase and replicate their DNA as they migrate toward each other. As they meet, the zygote enters M phase of its first mitotic division. The two nuclear envelopes break down, and the condensed chromosomes of both paternal and maternal origin align on a common spindle. Completion of mitosis then gives rise to two embryonic cells, each containing a new diploid genome. These cells then commence the series of embryonic cell divisions that eventually lead to the development of a new organism.

https://www.ncbi.nlm.nih.gov/books/NBK9901/

What occurs soon after fertilization is very complex, and is still being unraveled. An article from 2014:

https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC4021448/#:~:text=Following%20fertilization%2C%20the%20egg%20exits,male%20haploid%20pronucleus%20is%20formed.

A brief description of what happens after fertilization here, in plainer language:

For the first 12 hours after conception, the fertilized egg remains a single cell. After 30 hours or so, it divides from one cell into two. Some 15 hours later, the two cells divide to become four. And at the end of 3 days, the fertilized egg cell has become a berry-like structure made up of 16 cells. This structure is called a morula, which is Latin for mulberry.

During the first 8 or 9 days after conception, the cells that will eventually form the embryo continue to divide. At the same time, the hollow structure in which they have arranged themselves, called a blastocyst, is slowly carried toward the uterus by tiny hair-like structures in the fallopian tube, called cilia.

The blastocyst, though only the size of a pinhead, is actually composed of hundreds of cells. During the critically important process of implantation, the blastocyst must attach itself to the lining of the uterus or the pregnancy will not survive.

If we take a closer look at the uterus, you can see that the blastocyst actually buries itself in the lining of the uterus, where it will be able to get nourishment from the mother’s blood supply.

https://medlineplus.gov/ency/anatomyvideos/000025.htm

As to your to claim that regarding human gametes

Meiosis does again occur after fertilization, albeit 10-12 years after.

I think it's important to point out that this is not true across the board: what you say only applies to male humans. The germ cells of female humans undergo Meiosis I whilst we are still embryos.

Starting at 4 weeks of development, primordial germ cells begin differentiating into oogonia in the ovaries of female embryos. Once the oogonia are formed, they enter Meiosis I and undergo DNA replication to form primary oocytes. A future girl/woman's primary oocytes are formed by the 5th month of fetal life and remain dormant in a prophase of Meiosis I until later on when puberty commences.

This is why it's long been commonly said that girls/women are born with all our eggs already; indeed, we had all our gametes when we were still inside our mothers' wombs.

Recent research has suggested that females might be able to generate new ova later on in life, so the longstanding claim that we come into the world with all the eggs we'll ever have already in our ovaries might not be entirely accurate.

But that aside, as of the present day, it's still considered an established fact that only male humans begin germ cell meiosis and the process of gamete production at puberty.

To your main point: yes, the principal determinant of whether a human develops as male or female is whether the sperm cell that combines with an ovum in fertilization is either X or Y. But to me, your framing seemed to be trying to equate the creation of sperm cells in the testes - spermatogenesis - with the creation of sexed human offspring. This struck me as very simplistic, because obviously a whole lot more has to happen for even a potential sexed human life form to come into being than just guys making sperm.

Your framing also stuck me as sexist, because it seemed to me that you were attempting to play up and center the role that male humans play in determining the sex of offspring, and to downplay, sideline and overlook the female role as though it's secondary, minimal or even non-existent. After all, your comment focused solely on spermatogenesis, the process of making male gametes, and only mentioned one parent, the male one, the biological father. You continue demonstrating what to me looks like a sexist bias by in your recent post by claiming:

the conference of the SRY gene must be done during the father’s meiosis.

As though all there is to making a male child and becoming a father is generating sperm containing the SRY gene.

When the reality is, most human males make hundreds of billions or trillions of viable sperm in their lives, but not a single one of those innumerable sperm cells have any chance of leading to offspring of either sex without major contributions and efforts by someone female. For a human being of either sex to come into being requires that a sperm cell fuse with an ovum made by a female person, something we do only 13 times a year for only about half our lives, plus innumerable other contributions from the female person after that. The male role in human reproduction is to make sperm and to ejaculate it or have it removed from the testes with medical assistance. But for female people, maturing and releasing eggs is only a tiny portion of what human reproduction entails and requires of us. Minimizing or entirely ignoring what reproduction requires for the female half of the human race is something that I find all too many men engage in way too freely.

BTW, I am not accusing you of being sexist personally, or of having sexist intent. I'm just saying that your framing in this instance came off to me as sexist; indeed, it seemed reminiscent of what used to be called "male chauvinism" and a new iteration of efforts by males over the course of history to "big up men" in an area of life where nearly all the effort, cost, risk, pain and accomplishment is borne and done by females. But I admit, this might simply be due to my own perhaps skewed perceptions and heightened sensitivities. I have no idea what your intent was, and I do not mean to cast aspersions on you as a person.

One final point. I know that in the vanishingly rare instances when XX people have the SRY gene or fragments of it, the assumption is that the X chromosome containing the SRY or SRY fragments is from the father - and that some error occurred during meiosis of male gametes for this to happen. But has this been proven? Could it be that some ova somehow end up with SRY fragments? I have no idea is there's any way that this is possible, but it seems to me that the the male bias which regards males as the norm and always depicts males as the leading and central players in human endeavors that has run through medical science from the start has led to a lot of mistaken assumptions.