Main Difference – Maternal vs Paternal Twins
Maternal and paternal twins are two types of twins. The main difference between maternal and paternal twins is that maternal twins are genetically-identical whereas paternal twins are non-identical twins. Maternal twins are also called identical twins or monozygotic twins. They are formed by the splitting of the fertilized egg. They share the same placenta as well. However, the types of membranes that surround the fetus such as chorion and amniotic sac can be varied. Paternal twins are formed by the fertilization of two separate eggs from two separate sperms at the same time. However, paternal twins are a type of dizygotic twins or fraternal twins.
Key Areas Covered
1. What are Maternal Twins
– Definition, Formation, Characteristics
2. What are Paternal Twins
– Definition, Formation, Characteristics
3. What are the Similarities Between Maternal and Paternal Twins
– Outline of Common Features
4. What is the Difference Between Maternal and Paternal Twins
– Comparison of Key Differences
Key Terms: Bi-paternal Twins, Fertilized Egg, Maternal Twins, Paternal Twins, Placenta, Sperms
What are Maternal Twins
Maternal twins refer to twins developed from a single-fertilized egg and are alike in all genetic characteristics including the appearance and sex. Since the formation of these types of twins occurs through the splitting of the same fertilized egg, maternal twins are also called monozygotic twins. Maternal twins have the same genetic material. Therefore, they are called identical twins as well. Generally, maternal twins share the same placenta. Maternal twins are shown in figure 1.
Figure 1: Maternal Twins
The fetus is surrounded by two membranes in the womb known as chorion (outer membrane) and amnion (inner membrane). Depending on the stage of the zygote that splits, several types of maternal twins can be identified. They are described below.
- Dichorionic/Diamniotic twins: Each twin has its own placenta, chorion, and amniotic sac.
- Monochorionic/Diamniotic: Each twin shares placenta and chorion but, separate amniotic sacs.
- Monochorionic/Monoamniotic: Twins share the same placenta, chorion, amniotic sac.
Maternal twins are called as such as the division of the same egg is seen in these types of twins.
What are Paternal Twins
Paternal twins refer to the twins developed from separate fertilized eggs and are not identical in appearance and sex. Paternal twins are so called as two or several sperms from father are involved in the formation of these types of twins. These twins are also known as fraternal twins. Since two eggs are involved in the formation, paternal twins are also known as dizygotic twins. As fraternal twins are formed from two, separate fertilization events, they are not genetically identical. They share 50% of genetic similarity as siblings do. Therefore, they are a type of non-identical twins. Generally, parental twins have separate placentas. They are dichorionic-diamniotic, having separate chorions and amniotic sacs. Formation of the two types of twins is shown in figure 2.
Figure 2: Formation of Twins
Most twins in the world are paternal twins. The sex and the other characteristics of the paternal twins also vary as in other siblings of the same family. Thus, fraternal twins can be either girl/boy, boy/boy or girl/girl. Paternal twins are caused by hyper-fertilization. IVF also induces the formation of paternal twins.
The sperms can come from either same or different fathers in paternal twins. When the sperms come from different fathers, bi-parental twins are formed.
Similarities Between Maternal and Paternal Twins
- Maternal and paternal twins are two types of twins formed during the same pregnancy.
- Both maternal and paternal twins share some kind of a genetic similarity.
- The individuals in each type of twins have different fingerprints.
Difference Between Maternal and Paternal Twins
Definition
Maternal Twins: Maternal twins refer to the twins developed from a single-fertilized egg and are alike in all genetic characteristics including the appearance and sex.
Paternal Twins: Paternal twins refer to the twins developed from separate fertilized eggs and are not identical in appearance and sex.
Significance
Maternal Twins: Maternal twins are formed by the splitting of the fertilized egg.
Paternal Twins: Paternal twins are formed by the fertilization of mother’s eggs by several sperms of the father.
Type
Maternal Twins: Maternal twins are also known as identical twins or monozygotic twins.
Paternal Twins: Paternal twins are also known as fraternal twins or dizygotic twins.
Placenta
Maternal Twins: Maternal twins share the same placenta.
Paternal Twins: Paternal twins have separate placentas.
Chorionicity and Amniocity
Maternal Twins: Maternal twins can be either Di-Di, Mono-Di, Mono-Mono or conjoined twins.
Paternal Twins: Paternal twins are Di-Di twins.
Genetic Identity
Maternal Twins: Maternal twins have identical genomes.
Paternal Twins: Paternal twins have 50% identical genomes.
Appearance
Maternal Twins: Maternal twins are alike.
Paternal Twins: Paternal twins are like siblings.
Sexes
Maternal Twins: Maternal twins have the same sex as they are separated from the same fertilized egg.
Paternal Twins: Paternal twins may have both sexes as the fertilization occurs separately.
Blood Type
Maternal Twins: Maternal twins have the same blood type.
Paternal Twins: Paternal twins have different blood types.
Hereditary
Maternal Twins: Maternal twins are not hereditary.
Paternal Twins: Paternal twins are hereditary.
Occurrence
Maternal Twins: One-third of the twins in the world are maternal twins.
Paternal Twins: Two-third of the twins in the world are paternal twins.
Conclusion
Maternal and paternal twins are two types of twins that occur during the same pregnancy. Maternal twins are formed by the splitting of a fertilized egg in order to develop several fetuses. Thus, maternal twins are identical and monozygotic. Paternal twins are formed by the separate fertilization of eggs. They are non-identical and dizygotic. Therefore, the main difference between maternal and paternal twins is the degree of identity and the mechanism of formation.
Reference:
1. Lazy Grace . “Types of Twins : Identical, Fraternal & Unusual Twinning.” Twins UK, Available here.
2. “Cases of Bi-Paternal Twins: It Really Does Happen.” The Luxury Spot, 18 Mar. 2016, Available here.
Image Courtesy:
1. “821215” (CC0) via Pixabay
2. “Identical twins lg” By National Human Genome Research Institute – National Institutes of Health. National Human Genome Research Institute. “Talking Glossary of Genetic Terms.”Retrieved November 17, 2016, (Public Domain) via Commons Wikimedia
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