i love chemistry i love atoms and elements and molecules and compounds and hydrocarbons and reactions i fucking love chemistry You Cannot Understand My Love For Chemistry a book by me
Science and I sometimes have a weird relationship.
Sometimes I remember that science fuels war, war fuel sscience and war hurts, so I wish science didn’t exist. But then I remember that science has been and still is fundamental for human development, so I want science to stick around forever.
I saw this post and smiled with the cursor hovering over the heart button. But then I remembered.
I’m a twin.
I didn’t win.
It was a draw.
Twins don’t work like that.
Once a sperm encounters an ovum, the ovum’s walls change so that any other sperm won’t be able to access the ovum.
An ovum has half of the mother’s DNA. A sperm has half of the father’s DNA. If two sperms were able to get to the ovum, you would have three halves, which is absurd.
When it comes to conception, three can happen.
1. One ovum gets fertilized, resulting in one zygote. One fetus, one placenta.
2. One ovum gets fertilized, resulting in one zygote which splits into two or more and creates multiple zygotes with the same DNA. Multiple homozygous fetuses, one placenta. The twins will look identical at birth.
3. Sometimes multiple ova will be available for fertilization at the same time. If that happens, multiple different sperms will fertilize the ova and create multiple zygotes with different DNAs. Multiple heterozygous fetuses, multiple placentae. The twins will look different at birth.
tl;dr: It wasn’t a draw. Either the zygote decided to split up, or there were two zygotes.
I’m not quite sure what people don’t understand about the term ”identical twins”. Meaning the characters have the exact same chromosomes and therefor the exact same gender.
submitted by viralcatalyst
First off, ^ sex should be used instead of gender, since we’re talking about DNA.
Secondly… Science time.~
When an egg cell and a spermatozoon get together, they make a zygote. The zygote can split and create 2+ new zygotes with the same DNA, resulting in 2+ homozygous “identical” twins who have the same DNA, the same appearance at birth, and the same sex.
When 2+ egg cells and 2+ spermatozoa get together in the same instance, they create 2+ separate zygotes. These zygotes have different DNA since they were created by different gametes, so they will result in 2+ heterozygous twins who have different DNA, different appearance at birth, and possibly different sexes.
What determines a embryo’s sex (XX/XY) is the spermatozoon. The egg cell says “X”, while the spermatozoon can say either “X” or “Y”. To say nothing of intersexed embryos, which occur when the gametes send different “messages”!
That said… The person being referred to in OP is using the term “identical” incorrectly, indeed!