The Genetic Relationship Between Identical Twins


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Which is why identical twins are also called monozygotic. Since you both have the same DNA, this is almost like the two sets of children have the same moms but different dads. In fact, this is why at the DNA level they are really more like half siblings instead of first cousins.

They share 25% of their DNA (and genes) instead of the usual 12.5%. Identical twins share all of their genes and are always of the same sex. In contrast, fraternal, or dizygotic, twins result from the fertilization of two separate eggs during the same pregnancy. They share half of their genes, just like any other siblings. Fraternal.

Among identical twins, 80 percent of those surveyed reported feeling closer and more familiar with their twin than they did to their best friends, suggesting a strong genetic. To add to Jonathan Shearer’s succinct and excellent answer, if two sets of identical twins had children, their children, while legally first cousins, would genetically be full siblings! Both mothers are identical, and both fathers are identical, so the genetic result would be the same as if there were a single father and mother. Monozygotic (identical) twins share all of their genes, while dizygotic (fraternal) twins share only about 50 percent of them. So, if a researcher compares the similarity between sets of identical twins to the similarity between sets of fraternal twins for a particular trait, then any excess likeness between the identical twins should be due to genes rather than environment.

Identical twins are identical, right? After all, they derive from just one fertilized egg, which contains one set of genetic instructions, or genome, formed from combining the chromosomes of mother. There is an overfocus on twins as subjects in genetic vs. environmental research.

Ironically, even today after living through the ups and downs of my life as a twin in a non-twin world, my twin. Identical twins share the same set of genes, such as ones for thick eyelashes or a pointy nose – as well as the genes that boost risk for diseases. But. There is a common misconception that identical twins have identical DNA and, though they begin development with a matching genetic blueprint, differences in gene expression throughout life means that they differentiate more and more as they age.

Though still more similar than ordinary siblings, they are no longer as identical as one may believe. Identical twins, also known as monozygotic, are those who originate when only one sperm cell fertilizes one egg. This zygote (the egg along with the sperm cell) divides into two, forming two embryos with the same genetic material.

This results in two identical siblings that are born at the same time.

List of related literature:

Since identical twins (called monozygotic twins since they develop from one fertilized egg called a zygote) share all the same genetic material, researchers study them in order to examine the influence of genes on human traits.

“Barron's AP Psychology with Online Tests” by Robert McEntarffer, Allyson J. Weseley
from Barron’s AP Psychology with Online Tests
by Robert McEntarffer, Allyson J. Weseley
Barrons Educational Series, 2018

Identical twins have identical genes, so they should also have the same susceptibility to hereditary diseases; whereas fraternal twins (which originate from two separate, fertilized eggs) have no greater similarity in their heredity than brothers or sisters born at different times.

“Foods & Nutrition Encyclopedia, Two Volume Set” by Marion Eugene Ensminger, Audrey H. Ensminger
from Foods & Nutrition Encyclopedia, Two Volume Set
by Marion Eugene Ensminger, Audrey H. Ensminger
Taylor & Francis, 1993

b) Fraternal twins in same family are often different; identical twins reared apart

“Handbook of Life Sciences” by Patel, Sunil & Rukam S.Tomar
from Handbook of Life Sciences
by Patel, Sunil & Rukam S.Tomar
New India Publishing,

The differences between identical twins, who share identical DNA, and fraternal twins, whose DNA shows the same approximately 50% of overlap found in any two siblings, are particularly useful, because both types of twins share similar environments.

“Discovering Psychology: The Science of Mind” by John T. Cacioppo, Laura Freberg
from Discovering Psychology: The Science of Mind
by John T. Cacioppo, Laura Freberg
Cengage Learning, 2015

This arises because identical twins occur when a fertilised egg divides and forms two separate foetuses, which must, therefore, have the same genetic material.

“Health and Safety: Risk Management” by Tony Boyle
from Health and Safety: Risk Management
by Tony Boyle
Taylor & Francis, 2019

Identical twins (also called monozygotic twins) are twins who develop from the splitting of a single egg that was fertilized by a single sperm, and unlike other siblings, they are genetic copies of each other, sharing 100% of their genes.

“Psychology” by Daniel L. Schacter, Daniel T. Gilbert, Daniel M. Wegner
from Psychology
by Daniel L. Schacter, Daniel T. Gilbert, Daniel M. Wegner
Worth Publishers, 2010

For example, twin families include monozygotic twins (identical twins), whose genetic material (i.e., DNA) is basically identical because they developed from the same fertilized egg, or dizygotic twins (fraternal twins), who developed from two different fertilized eggs.

“Human Intelligence: An Introduction” by Robert J. Sternberg
from Human Intelligence: An Introduction
by Robert J. Sternberg
Cambridge University Press, 2019

Fraternal twins are better than full siblings for exploring associations between DNA markers and traits of interest (linkage studies) because fraternal twins are the same age and less likely to pose nonpaternity concerns—although recall that we do not know how often fraternal twins have different fathers.

“Twin Mythconceptions: False Beliefs, Fables, and Facts about Twins” by Nancy L. Segal
from Twin Mythconceptions: False Beliefs, Fables, and Facts about Twins
by Nancy L. Segal
Elsevier Science, 2017

Identical twins those originating from a single egg have exactly the same genes as each other; while fraternal, or dizygotic, twins are of no greater similarity to one another than to any other sibling from the same parents.

“The Singing Neanderthals: The Origins of Music, Language, Mind, and Body” by Steven J. Mithen
from The Singing Neanderthals: The Origins of Music, Language, Mind, and Body
by Steven J. Mithen
Harvard University Press, 2006

The twin method allows such traits to be studied based on the principle that human twins are of two basic types: monozygotic (or identical) twins, resulting from a single ovum fertilized by a single sperm, and dizygotic (or fraternal) twins, resulting from fertilization of two ova by two sperms.

“McDonald and Avery's Dentistry for the Child and Adolescent E-Book” by Jeffrey A. Dean
from McDonald and Avery’s Dentistry for the Child and Adolescent E-Book
by Jeffrey A. Dean
Elsevier Health Sciences, 2015

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 saw a story, where these girls were twins, but one was white and one was black. And the father was black as the Mom is white. What do you call that? I hope I explained clearly lol

  • I’m an identical twin,… we get along ok, but this seems so unhealthy to me, on so many levels. Having no personal identity for starters then, turning your life into a sports event is unnerving.

  • I do wish my twin sister identical twin sister was here to see what it would be like but I know when shes here with me because the bond her and I had we still have even though she isn’t here. When I’m writing my hand writing changes and it’s because my twin sister loves to write as well

  • yes l am a twin and we do a lot of things the same like cooking the same go shopping the same hour we look alike and we love each other very much

  • I have male twins, which they were my little cousins. The elder twin has a large round mole on his left lower leg and the youngest twin has a tall yet slightly thin figure.. they’re both tall and thin but the older twin was much a bit chubby tho

  • I have an identical twin, we were triplets but my mom lost it b4 she even knew she was pregnant. I wonder if it would b a girl or a boy and if it was a girl would we all look alike ��

  • Awesome. There have been twins living together. I have twin step sons & they live together with their wives. There wives r not twins but they sure do look alike

  • I looked in the mirror and saw my twin. When I get married I’m going to have a big mirror so my twin will get married the same time as me.