How Monozygotic Twins Develop


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Monozygotic twins are formed when one zygote, created with one egg and one sperm, splits into two. Instead of having just one embryo—which is usually what you get from one egg and one sperm—the result is two embryos. Each of those embryos develops as a separate fetus.

Monozygotic twins form from a single fertilized egg that splits to form two embryos that develop into two babies. Because the two individuals originate from a single source, they share the same genetic components and may exhibit amazing similarities. Thus, they’re considered “identical.”. Monozygotic twins can develop by splitting in the early cell stage developing into two zygotes, in the early blastocyst stage allowing them to share the placenta and chorionic cavity, or at the bilaminar germ disc stage allowing them to share a single placenta, chorionic sac, and amniotic sac.

References and External Links. Monozygotic twins, also known as identical twins, develop from one egg fertilized by one sperm. The frequency of monozygotic twins is around 1 in 250 pregnancies without assisted fertility. Identical twins begin as a single egg that has been fertilized by a single sperm.

From that beginning, the egg will split into two. Monozygotic twins _ a. are genetically no more alike than any siblings. c. develop from a single fertilized ovum. b. can be same-sex or opposite-sex. d. are often joined at one area of the. However, DNA fingerprinting has become the only accurate method to dif­ferentiate between Monozygotic and Dizygotic twins. The monozygotic twins are genetically identical and any discordance between them is due to environmental influences whereas diffe­rences within dizygotic twin pairs are likely to be a combination of genetic and environmen­tal factors.

Identical twins develop after your fertilized egg splits in half and creates two genetically identical (aka monozygotic) embryos. If this happens a couple of weeks after conception, then each baby gets his or her own gestational sac and placenta. The second kind of twins, which stem from a single oocyte, are known as monozygotic twins or “real twins” (the frequency amounts to 3 to 4 in 1000 deliveries). They result from a division of the blastomeres in various stages of their development.

Monozygotic and dizygotic twins are two main types of twins. As the names suggest, monozygotic twins develop from one zygote while dizygotic twins develop from two separate zygotes. Therefore, this is the key difference between monozygotic and dizygotic twins.

Monozygotic twins originate due to the splitting of the zygote into two halves randomly. Fraternal twins develop from two eggs that are released and fertilized at the same time by two different sperm. They’re known as dizygotic (DZ).

Identical twins develop from one egg that splits into two and are known as monozygotic (MZ). Because they come from the same egg, so-called “identical” twins.

List of related literature:

Identical or monozygotic twins come from a single egg cell fertilized by a sperm cell which splits into two; while fraternal comes from two eggs released at the same time and fertilized by two sperms.

“Introduction to Psychology”
from Introduction to Psychology
Macmillan and Company, Limited, 1916

Monozygotic twins (MZ) result from one ovum fertilized by one sperm that then divides to form two embryos.

“Emery and Rimoin's Essential Medical Genetics” by David L. Rimoin, Reed E. Pyeritz, Bruce Korf
from Emery and Rimoin’s Essential Medical Genetics
by David L. Rimoin, Reed E. Pyeritz, Bruce Korf
Elsevier Science, 2013

For monozygotic twins to develop, one sperm fertilizes one egg, and the zygote then splits.

“The Human Body in Health and Illness E-Book” by Barbara Herlihy
from The Human Body in Health and Illness E-Book
by Barbara Herlihy
Elsevier Health Sciences, 2014

Monozygotic twins ought to be identical because they originate from the same ovum fertilized by a single sperm, but separate into two zygotes during the first thirteen days, whereas fraternal (dizygotic) twins are formed when two eggs are fertilized by two sperm.

“The Big Book of Reincarnation: Examining the Evidence that We Have All Lived Before” by Roy Stemman
from The Big Book of Reincarnation: Examining the Evidence that We Have All Lived Before
by Roy Stemman
Hierophant Publishing, 2012

Triplets can occur from the division of one zygote into two, with one dividing again, producing identical triplets, or they can come from two zygotes, one dividing into a set of identical twins, and the second zygote developing as a single fraternal sibling, or from three separate zygotes.

“Maternity and Pediatric Nursing” by Susan Scott Ricci, Terri Kyle
from Maternity and Pediatric Nursing
by Susan Scott Ricci, Terri Kyle
Wolters Kluwer Health/Lippincott Williams & Wilkins, 2009

Identical twins (or monozygotic twins) are twins who develop from the splitting of a single egg that was fertilized by a single sperm, and fraternal twins (or dizygotic twins) are twins who develop from two different eggs that were fertilized by two different sperm.

“Psychology: Second European Edition” by Daniel Schacter, Daniel Gilbert, Daniel Wegner, Bruce Hood
from Psychology: Second European Edition
by Daniel Schacter, Daniel Gilbert, et. al.
Palgrave Macmillan, 2015

Monozygotic twins (so-called identical twins) (approximately 30%) are generated by division of a zygote that originated from the fertilization of one single ovum by one single sperm cell.

“Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice E-Book” by Robert Resnik, Charles J. Lockwood, Thomas Moore, Michael F Greene, Joshua Copel, Robert M Silver
from Creasy and Resnik’s Maternal-Fetal Medicine: Principles and Practice E-Book
by Robert Resnik, Charles J. Lockwood, et. al.
Elsevier Health Sciences, 2018

Monozygotic twins result from the ovulation and fertilization of one oocyte then followed by division of the zygote.

“Klaus and Fanaroff's Care of the High-Risk Neonate E-Book” by Jonathan M Fanaroff, Avroy A. Fanaroff
from Klaus and Fanaroff’s Care of the High-Risk Neonate E-Book
by Jonathan M Fanaroff, Avroy A. Fanaroff
Elsevier Health Sciences, 2012

monozygotic twins, two offspring born of the same pregnancy and developed from a single fertilised ovum that splits into equal halves during an early cleavage phase in embryonic development, giving rise to separate fetuses.

“Mosby's Dictionary of Medicine, Nursing and Health Professions Australian & New Zealand Edition eBook” by Peter Harris, Sue Nagy, Nicholas Vardaxis
from Mosby’s Dictionary of Medicine, Nursing and Health Professions Australian & New Zealand Edition eBook
by Peter Harris, Sue Nagy, Nicholas Vardaxis
Elsevier Health Sciences, 2014

• Monozygotic twins develop when a single fertilized ovum splits after conception.

“Pediatric Board Study Guide: A Last Minute Review” by Osama I. Naga
from Pediatric Board Study Guide: A Last Minute Review
by Osama I. Naga
Springer International Publishing, 2019

Oktay Kutluk

Kutluk Oktay, MD, FACOG is one of the world's foremost experts in fertility preservation as well as ovarian stimulation and in vitro fertilization for infertility treatments. He developed and performed the world's first ovarian transplantation procedures as well as pioneered new ovarian stimulation protocols for embryo and oocyte freezing for breast and endometrial cancer patients.

Mail: [email protected]
Telephone: +1 (877) 492-3666

Bibliography: oktay_bibliography

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  • I tuned in looking at reviews of Tahiti Village… (we are headed there tomorrow) but then I got to see you bring a couple beautiful people into this world! what a treat! Congratulations Mom & Dad!!!

  • Just found out I’m having twins and I love watching videos like this because I don’t want to be blind sided. Also the joy you had in your eyes when the babies finally came out gave me hope in case I have to have a c section.

  • OH My, i was so nervous because she was shaking so much. but after first baby Came out she stop shaking AND then I think ok, she Is ok.

  • Congratulations guys I’m so happy you okay thank god I’m due in March I’m also having twins I’m scared of a c C-section but if I have to do it I’ll do it thank you for sharing your journey wit us

  • I didn’t like the way they talked to you but you did such a wonderful job you should be proud. Those kids are going to grow up beautifully

  • Wow! Im so sad that they talked to you like that when i had my 1st c section i was like half asleep and didnt feel anything which was good cause my anxiety kicked in bad before they took me to the operating room i started crying and breathing heavy shaking telling them i cant do it im scared but by the time i knew it i heard my baby crying then i fell in a deep sleep and woke up in recovery rest my sons soul���� now im expecting again and scheduled a c section exactly on my birtday i hope it goes well and you completely didnt deserve that at all!! Im so glad you spoke up….

    I just realized your babies were born a day after my son he was born june 11, 2019 and passed june 18th 2019

  • Great weights for 35 week twins. If you would have made it to 39, they would almost be single baby weights! Good job mom on giving them good nourishment during pregnancy.

  • I know y’all are crazy-busy. Please do a “first b-day” vid when y’all are up to it. Your subs miss you!!
    Stay safe and Best wishes, Ozzie and Anna!! ��

  • This video made me �� cry. I’m a proud Granma of identical twin girls and as I’m seeing everyone’s emotions on your video I was remembering mines. My girls are Jaylanny and Kaylanny and they are going to be 2 in July. I don’t know how old this video is but I want to regardless congratulate you. Twins are a blessing!!

  • Thank you for sharing this video. I am pregnant with twins and I am happy that I watched this video. Congrats and you look just fine.:)-

  • Beautiful women beautiful baby girls congratulations you are both parents. Good luck on parenting and your wonderful journey with your babies ik I’m late on a comment and I’m sorry for that

  • I gave birth to my identical twin boys, who are now 2, and I will never forget how rude my doctor was…he also only showed me one of my sons and not the other, even though they were both healthy boys:) luckily my husband recorded everything!

  • I’m currently 23 weeks pregnant today and I’ve been having so much anxiety of having to think of getting a c-section because of the pressure and not knowing whats on the other side. You are a strong mom�� and I hope I can be strong as you.

  • I was also born via C-section and my mom died on the operating table when they took me out. They did revive her after 3 tries. I will be turning 32 this July 30th and my mom’s birthday is after that. She always says I was her birthday present

  • I had anesthesia with my emergency one. When the doc did the first cut i felt it the medicine had got kicked in until 3 seconds after i felt that sharp pain of the knife cutting me i screameddd out in pain. then i was in a dream like state. It was like i was woke but was not i still felt tugging and pressure. Every now and then it truly felt like a dream. I really woke up when i heard baby crying and don’t rem anything after that. I think they could have reassured u more than to be talking about as if they were not delivering babies. Coule have been more caring about it. But congrats u didvery well. My worst part was when they checked me to see how far i was dilated was pure pain

  • Ughhh I hate when doctors are like that, there’s no need to be rude. I tolerated so much when I had my first baby to rude nurses, late doctors. But nah I’m not taking none of that this time. They are paid for the job they do, they have to be calm and nice.

  • Aloha! I’m a newbie to your channel, actually found you when I was searching for Chinatown in Vegas lol! Congrats on your two precious bundles of joys, what a beautiful family ☺️❤️. Thanks for sharing!

  • I love this video ���� I felt as if I was right there wit you guys, you did an amazing job and your husband was so supportive, I love that and y’all daughters are so beautiful ����… thanks for sharing this journey with us, cuz it is preparing me for that day, this was very helpful & I am ready for my day to finally be able to meet my identical twin boys ����

  • Hey guys I just re-watched this vid because your “quarantine Easter” video reminded me to. ; ) I loved it even more this time around and noticed details I didn’t notice the first time around (both content-wise and in your technique). And yeah, I cried even more than I did the first time around, lol Because thanks to your videos since you posted this, I’ve seen you and your babies as y’all are now; heard your Mom’s voices in your April Fool’s video (and I assume that’s them in the parts at the end); seen your beautiful family and what a great team you and Ozzie were both then and how you’ve grown even stronger since. Thank you!
    Please let us subs know how we can support you better! BTW, my $.02 tip: Whenever you post a family vid with Saylor and Sunday, include a balloon that points to this video (sorry I don’t know what “YouTube-speak” word it’s called, but lots of other YTers do it) and mention that if anyone wants to see the day they were born, to click on it. Just sayin’….
    Anywho, love y’all and stay safe!! ���� I can’t wait to see your next video, whatever it is!! ; )

  • I understand her fear and anxiety every thing she is going through. C-sections is no joke! Had my twins as my third births…..very traumatic

  • My wife was the one keeping me calm i was scared shitless at her shaking i didnt watch no videos or educate myself because i didnt think they would have to do a c section

  • I had my c section too but I didn’t feel any kind of pain.for me c section was better than normal delivery because before c section I did go through all the normal delivery pain

  • You are an amazing, strong and beautiful woman. You both did great…and with the love you share will be great parents. The girls are so precious! Congratulations! ��������������

  • I thought you were kidding congratulations I didn’t even watch the other video I don’t know if you get a pregnancy test but congratulations

  • Congratulations ������Thank you for sharing that! I can relate to your nervousness. I had a csection and was so nervous myself. But you did awesome and your babies are beautiful!

  • C sections are no joke. I hate when doctors talk to you like your crazy and annoying for being scared. I have anxiety about death and needles and blood and it makes it soooooo much worse.

  • I was actually a little upset at how the anesthesiologist and doctor were talking to you, and the fact that other staff were also arguing in the background. I wanted to rush in and tell them to stop and to reassure you. Your husband did a great job and I am glad for you that this part is over and you have 2 beautiful babies to show for it. I hope you are all doing well. They have beautiful names, congratulations!

  • I had a c section too and on they told me that their was going to be pressure I calm down and relaxed it felt weird but just knowing my Lil one was coming I was so happy

  • Awe honey, I feel so bad for you the way the doctor was speaking to you. This is so scary for someone. Especially a first time mama. I feel like he should have known how scared you where but he did settle down thank god and you did amazing! Thank you for documenting this and sharing and glad everything went beautiful and beautiful babies!!! Wow!

  • I have never had surgery and would be terrified too, knowing they were cutting my whole gut open and digging two humans out. Your feelings of fear were beyond valid. I would have asked them 100 times to verify I was numb through and through.

  • Omg i have c section scheduled in 3 weeks and omg seeing this make feel so much better cause it’s ok to feel stressed and anxious it’s good to know I’m not the only one

  • I was given general anesthesia for my twin birth…I could only touch or see my babies after 24hours….I felt bad I cldnt see or touch them immediately they came out… But thank God for d gift

  • Congrats this is what I’m scared of I am also pregnant with twins and I’m so scared of a c section your a very strong women god bless you both and those sweet baby’s ❤️❤️❤️❤️

  • Having an elective c section next week and come to YouTube.. I cried through this video as I feel so upset the anxiety is crazy and I’m. Not. There yet!

  • Plus I just came back from Las Vegas //your the reason why I went to Frankie’s tiki bar //what a great place got my first tiki mug ������

  • Awwww congrats! My mom is pregnant with identical dye dye twin girls! We are so exited and can’t stop watching twin videos!

    Also…I’m a small YouTuber trying to grow my family friendly channel! Feel free to subscribe❤️

  • AWESOME. CONGRATS!!!!!! I have a feeling we will be watching these two grow up. That’s fine with me. I have twin granddaughters. They are 20 years old. Love them to pieces.

  • Wowww, c sections are no joke. You did so good through it all…and I have to say you looked amazing, so beuatiful. Congrats u 2!! ��������‍��‍��‍��������☝️☝️��������

  • Don’t like how they treated you it’s normal to be worried about feeling it they could have handled that better but congratulations so happy for you

  • Thank you for sharing that with us they are so beautiful and amazing names the feeling pressure thing scared the crap out of me as well with my fist one you did great

  • This is clearly a timed presentation where you have to get as much info in as possible in a certain amount of time, or you will get marked down for going over the time. Anyone who has been to Uni knows.

  • She’s Arab (see the name) they do nothing right, not even spell their names correctly, using the Latin alphabet.

    ….Slow down, dear, you’re not in a race (you’ve just ruined the whole video)!