Objective To investigate the relationship between the first polar body morphology of oocyte and the zygote morphology in pronucleus stage, embryo quality in cleavage stage.
On the inside, the fallopian tubes have smooth muscle with an inner lining that has ciliated cells that slowly sweep the secondary oocyte or zygote towards the uterus.
Once the sperm arrives, it fuses with the egg to make a zygote — a cell that contains all the DNA needed to make a baby, thanks to the combination of the two DNA halves.
一旦精子到达,它就会与子融合,形成受精——由于两半 DNA 的结合,受精包含了制造婴儿所需的所有 DNA。
But for now you learned about the four phases of the human sexual response, how a sperm finds and fertilizes an egg, creating a zygote, and how different types of contraception work to prevent that from happening.
First, they all start as single-celled zygotes — made from a sperm cell and egg cell combo — that become multicellular embryos: the tiny beginnings of roots, stems, and leaves.
When the membranes of the two pronuclei rupture, chromosomes go flying, and boom, you officially have a diploid zygote, which almost immediately starts mitosis.
This specialization makes DNA from non-sex cells particularly unsuited for cloning purposes because those tags and tangles make it hard for the clone zygote to divide.
Cloned zygotes are not reliable because while all other cells in the body do contain a full set of DNA, these other cells optimize their DNA to best serve their own particular functions.
克隆的受精并不可靠,因为虽然体内所有其他细胞确实含有全套 DNA,但这些其他细胞会优化其 DNA 以最好发挥其自身的特定功能。