[MHGinTN]

And I would assert that conception is when the embryonic being implants in the uterine lining (or elsewhere in the case of ectopic implantations). The reason your assertion is wanting is because the embryo at the stage of zygote can become more than one individual human being. BUT upon implantation there is the one (sometimes having a second implantation very close and rarely two or more combine to form a chimera).[ I have a little free book at my blogpage which explains the biology for laymen, if you need to consult it. The link is on my profile page. Feel free to download it; more than 10,000 have done so already. ]

The ONE WHO was implanted/conceived in Mary is Jesus, by the authority of the Scriptures we may make that assertion. We cannot make an inference that GOD used Mary's chromosomes to create the body for Jesus. God did not give us the specifics to that level of certainty.

[ebb tide]

You prots really like to cherry-pick scripture, don't you?

[31] Behold thou shalt conceive in thy womb, and shalt bring forth a son; and thou shalt call his name Jesus. [32] He shall be great, and shall be called the Son of the most High; and the Lord God shall give unto him the throne of David his father; and he shall reign in the house of Jacob for ever. [33] And of his kingdom there shall be no end. Luke Chapter 1 [emphasis mine].