Opposite twins are often referred to as mirror twins or mirror image twins. This is because they are identical twins who develop with opposite features on either side of their bodies, as if they were a reflection of each other. For example, one twin may have a birthmark on their left arm, while the other twin will have a birthmark in the same location but on their right arm.
Mirror twins can also have opposite dominant hands or even opposite eye colors in rare cases. They occur when the fertilized egg splits later than usual during the early stages of development, causing mirror image features to occur. While mirror twins are rare, they are fascinating and often show how genetics can manifest in unique ways.
Table of Contents
What are the 7 types of twins?
Twins occur when a single fertilized egg splits into two embryos. The process of twinning can occur at different stages, which result in different types of twins. There are seven types of twins that can be classified based on the number of fetuses (two or three), the timing of division, and the location of the fertilized egg.
These seven types of twins are:
1. Identical (monozygotic) twins: These twins are formed when a single fertilized egg splits into two identical embryos. They share the same genetic material, hence are also known as monozygotic twins. Identical twins have identical physical features, such as hair and eye color, and are always of the same sex.
They may or may not have matching fingerprints.
2. Fraternal (dizygotic) twins: Fraternal twins occur when two eggs are released during ovulation and fertilized by two different sperm. These twins are not genetically identical, as they come from two different eggs. Fraternal twins can be of the same or different sexes, and can have different physical features such as hair and eye color.
3. Semi-identical twins: Semi-identical twins are a rare type of twins that are formed when one egg is fertilized by two sperm, resulting in three sets of chromosomes instead of the usual two. This type of twinning is also known as polar body twinning.
4. Monoamniotic twins: Monoamniotic twins occur when one fertilized egg splits into two embryos, but they share the same amniotic sac and placenta. This type of twinning is considered high-risk, as the twins are at risk of getting entangled in each other’s umbilical cords.
5. Monochorionic twins: Monochorionic twins are identical twins that share the same placenta but have separate amniotic sacs. This type of twinning is considered high-risk, as the twins may develop twin-to-twin transfusion syndrome.
6. Conjoined twins: Conjoined twins are identical twins that are physically attached to each other. This happens when the separation of embryos is incomplete. Conjoined twins can be classified into different types depending on their location of attachment, such as thoracopagus (joined at the chest) and craniopagus (joined at the head).
7. Identical triplets: This occurs when a single fertilized egg splits into three identical embryos. Identical triplets are rare, and occur in approximately 1 in 5 million births.
The seven types of twins include identical, fraternal, semi-identical, monoamniotic, monochorionic, conjoined, and identical triplets. Each type of twin has its own unique characteristics and risks.
How many different kinds of twins are there?
There are several different types of twins. The most common type is fraternal twins, which occur when two separate eggs are fertilized by two separate sperm. Fraternal twins can be of the same sex or different sexes and they do not share the same genetic material.
Another type of twinning is identical twins, which occur when a single fertilized egg splits into two separate embryos. Identical twins are always of the same sex and they have nearly identical genetic material. Twins that share a placenta and amniotic sac are called monoamniotic-monochorionic twins or sometimes referred to as “identical” twins, but they are actually monozygotic twins that have a single placenta and amniotic sac.
There are also several rare types of twins, such as conjoined twins, which occur when the embryos do not fully separate and some parts of their bodies are fused together. Additionally, there are semi-identical twins, which occur when a single egg is fertilized by two sperm, resulting in three sets of chromosomes instead of the typical two.
These types of twins are extremely rare and there have been only a handful of cases reported worldwide.
Overall, there are different types of twins depending on how they are formed and how their genetic material is shared. Each type of twinning is unique and has its own set of challenges and possibilities.
Which parent decides twins?
The answer to this question relies on whether the twins are fraternal or identical. Fraternal twins, also known as dizygotic twins, occur when two eggs are released and fertilized by two different sperm. In this case, it is not determined by a specific parent as the mother releases two eggs during ovulation that can possibly be fertilized by two different sperm.
Therefore, fraternal twins are a result of chance rather than genetics.
On the other hand, identical twins, also known as monozygotic twins, occur when a single fertilized egg splits into two embryos. This type of twinning is not influenced by either parent’s genetics, but rather is a spontaneous occurrence. It is not entirely clear what triggers the splitting of the fertilized egg, but it is believed to be a random event that happens early in development.
While neither parent directly determines whether twins are fraternal or identical, the likelihood of having fraternal twins may be influenced by certain factors such as age, fertility treatments, and certain fertility drugs. However, the occurrence of identical twins is purely a chance event and cannot be predicted or influenced by any external factors.
Which type of twin is inherited?
There are two types of twins: identical (monozygotic) twins and fraternal (dizygotic) twins. Identical twins result from the fertilization of a single egg by a single sperm, which then divides into two identical embryos. Fraternal twins, on the other hand, result from the fertilization of two separate eggs by two separate sperm.
The type of twin that is inherited depends on several factors. Identical twins are not inherited in the traditional sense because they occur randomly and are not influenced by genetics. However, there may be some genetic factors that increase the likelihood of fraternal twins.
One of these factors is a woman’s age, with older women being more likely to release more than one egg during ovulation, increasing the chances of fraternal twins. Additionally, having a family history of fraternal twins can increase the likelihood of having fraternal twins yourself.
Overall, while the occurrence of identical twins is not influenced by genetics, there are some genetic factors that can increase the likelihood of fraternal twins.
Are fraternal twins the most common?
Fraternal twins, also known as dizygotic twins, are the most common type of twins. They occur when two separate eggs are fertilized by two different sperm, resulting in two genetically distinct embryos. Fraternal twins can be of the same or opposite sex and have varying degrees of similarity in their physical appearance and personalities.
Statistically, fraternal twins account for about two-thirds of all twin pregnancies. This is because they are the result of a natural process of ovulation, where the woman releases two eggs instead of one during her fertile period. It is also possible to conceive fraternal twins through fertility treatments, where multiple embryos are transferred to the uterus.
On the other hand, identical twins, also known as monozygotic twins, occur when a single egg fertilizes and divides into two separate embryos. This happens in about 1 in every 250 pregnancies. Identical twins share the same genetic makeup and are typically of the same sex. They can have very similar physical features and personalities, making it difficult for others to tell them apart.
While both fraternal and identical twins occur naturally, fraternal twins are the most common type of twins due to the natural occurrence of releasing two eggs during ovulation. However, the occurrence of twin pregnancies can also be influenced by age, family history, and other factors.
What type of twins have 100% of their genes in common?
The type of twins that have 100% of their genes in common are identical or monozygotic twins. Identical twins occur when a single fertilized egg (zygote) splits into two separate embryos, each with the same genetic material. As a result, identical twins have identical DNA and share all of their genes, making them monozygotic.
This means that they are essentially clones of each other, and their physical traits, behavioral patterns, and susceptibility to diseases are mostly identical. Identical twins are always of the same sex and have indistinguishable physical features, making it difficult for people around them to tell them apart.
Studies and research on identical twins have played a significant role in medical research as they help to understand the role of genetics in various diseases and disorders that can affect humans. Identical twins can have many similarities, but their personalities and experiences can differ just like any other siblings.
Nonetheless, they share an exceptional bond, similar to other twins, and it is fascinating to see how they interact and relate to each other.
How common are fraternal twins?
Fraternal twins are fairly common as compared to identical twins. Fraternal twins are also known as dizygotic twins, are the result of the fertilization of two separate eggs by two different sperm cells. Thus, they are not genetically identical and can be of the same sex or different sexes. According to a report by the National Center for Health Statistics, in the United States in 2018, the rate of fraternal twin births was 17.4 per 1,000 total births.
This means that about 1 in every 29 babies born was a twin.
There are certain factors that increase the likelihood of having fraternal twins, including maternal age, family history, ethnicity, fertility treatments such as in vitro fertilization (IVF), and the use of ovulation-stimulating medications. For instance, women who are over the age of 35, are of African descent, and have a family history of fraternal twinning are more likely to have fraternal twins.
In addition, women seeking fertility treatments to conceive, such as IVF or ovulation-inducing medications, have an increased chance of having fraternal twins.
Fraternal twins are not an uncommon occurrence, and their incidence rates are affected by various factors such as maternal age, ethnicity, family history, and medical interventions such as fertility treatments. Although fraternal twins may run in some families, it is not always guaranteed that each pregnancy will result in twins.
Therefore, it is essential to be aware of the risk factors and options available for those who wish to conceive or may be at higher risk of having fraternal twin pregnancies.
Can fraternal twins be identical?
In general, fraternal twins cannot be identical. Fraternal twins, also known as dizygotic twins, form when two separate eggs are fertilized by two separate sperm. This means that each twin has their own distinct genetic makeup, just like any other siblings that are born at different times. While fraternal twins can share some similarities due to their shared environment in the womb, they can have different hair and eye colors, different blood types, and even different sexes.
However, there are rare cases where fraternal twins can appear identical. This can occur when the two eggs are fertilized by the same sperm, and then split into two embryos. This is known as polar body twinning, and it can result in fraternal twins who have nearly identical DNA. However, polar body twinning is extremely rare and estimates suggest that it occurs in only about 1% of fraternal twin pregnancies.
Another reason why fraternal twins may appear identical is if they are a mix of two different types of twins. For example, if a fraternal twin pair is made up of one boy and one girl, and the girl also has Turner syndrome (a genetic condition that affects females), she may have some physical features that are more typical of males.
This could lead people to mistake the fraternal twin pair for identical twins, even though they are not.
Overall, while it is possible for fraternal twins to appear identical due to very rare circumstances, it is more likely that they will have different genetic makeups and physical features. Therefore, in most cases, fraternal twins cannot be identical.
Which is more rare identical or fraternal twins?
Identical and fraternal twins are both types of multiple births. Identical twins are formed when a single fertilized egg splits into two separate embryos, while fraternal twins are formed when two separate eggs are fertilized by different sperm.
Statistically, identical twins are considered more rare than fraternal twins. According to the National Organization of Rare Disorders, approximately 0.4% of all pregnancies result in identical twins. In contrast, fraternal twins occur in approximately 1.6% of all pregnancies. This means that approximately 4 out of 1000 pregnancies result in identical twins, while 16 out of 1000 pregnancies result in fraternal twins.
The rarity of identical twins can be attributed to the fact that they are a result of a random, spontaneous event in which a single fertilized egg splits into two embryos. Fraternal twins, on the other hand, are more likely to occur in certain populations or under specific circumstances, such as when a woman is undergoing fertility treatments or is over the age of 35.
While identical twins may be considered more rare than fraternal twins, both types of twins can have a significant impact on the lives of those involved. Twin births are often associated with increased medical risks for both the mother and the babies, including premature birth, low birth weight, and developmental issues.
Additionally, twins often share a special bond and experience unique social and emotional challenges that arise from being part of a multiple birth.
Can a boy and a girl be identical twins?
No, a boy and a girl cannot be identical twins. Identical twins, also known as monozygotic twins, are formed when a single fertilized egg splits into two embryos during early development. As a result, the two embryos have the same genetic material and therefore are of the same sex. In other words, identical twins are always of the same gender, either both male or both female.
On the other hand, fraternal twins, also known as dizygotic twins, are formed when two separate eggs are fertilized by two separate sperm cells. Fraternal twins may be of the same gender, in which case they are referred to as same-sex twins, or of different genders, in which case they are referred to as opposite-sex twins.
Therefore, while it is possible for a boy and a girl to be twins, they cannot be identical twins. They would be fraternal twins who happen to be of different genders. It’s important to note that fraternal twins may or may not share the same genetic material as they are formed from different fertilized eggs.
Are Mary Kate and Ashley identical or fraternal?
Mary-Kate and Ashley Olsen are fraternal twins. Fraternal twins are formed when two different eggs are fertilized by two different sperm. As a result, they do not share the same genetic material, and can therefore have different physical features and personalities. Mary-Kate and Ashley may look similar, but there are noticeable differences between them, including their height, weight, and facial features.
It is also important to note that Mary-Kate and Ashley have their own preferences and interests, and have pursued different careers in fashion and acting. While the term “identical twins” is often used to describe any set of twins that look alike, it is only applicable to twins that share the same genetic material and are formed from a single fertilized egg that splits in two.
Mary-Kate and Ashley are fraternal twins, and are not identical.
Can an ultrasound tell if twins are identical or fraternal?
Yes, an ultrasound can help determine if twins are identical or fraternal, however, it is not always 100% accurate.
Identical twins occur when a fertilized egg splits into two embryos, resulting in two genetically identical babies. Fraternal twins, on the other hand, occur when two separate eggs are fertilized by two different sperm, resulting in two genetically different babies.
One way to determine if twins are identical or fraternal is by looking at their placenta. Identical twins share a placenta while fraternal twins have separate placentas. An ultrasound can help in visualizing the placenta and identifying if there is one or two present.
However, in some cases, identical twins may have separate placentas, especially if the splitting of the fertilized egg occurs later in development. In such cases, an ultrasound may not be able to accurately determine the type of twins present.
Another way to determine if twins are identical or fraternal is by comparing their physical characteristics. Identical twins will look very similar, often having the same eye and hair color as well as the same facial features. Fraternal twins, on the other hand, may look different from each other, just like any other siblings.
With advancements in technology, there are also DNA tests available to determine if twins are identical or fraternal. These tests are more accurate than ultrasound or physical characteristics comparisons.
An ultrasound can be a helpful tool in determining if twins are identical or fraternal, however, it may not always provide 100% accurate results. Comparison of physical characteristics and DNA testing can also aid in determining the type of twins present.
Can 2 sperm fertilize the same egg?
No, it is impossible for two sperm to fertilize the same egg. This is due to the natural process of fertilization, which involves the fusion of one sperm with one egg, resulting in the creation of a zygote.
During fertilization, a woman’s body releases one mature egg each month from her ovaries, which then travels down the fallopian tube towards the uterus. At the same time, sperm from the male partner are introduced into the female reproductive system, where they swim towards the egg.
The outer layer of the egg, called the zona pellucida, helps to prevent more than one sperm from entering the egg. As soon as one sperm penetrates the zona pellucida and fertilizes the egg, the outer layer hardens, creating a barrier to prevent any more sperm from entering.
This process is known as polyspermy and is considered abnormal, as the resulting embryo would likely have too many genetic abnormalities to survive. In rare cases, the zona pellucida may be compromised by fertility treatments, causing more than one sperm to enter the egg, but this only occurs in less than 1% of cases.
While it is impossible for two sperm to fertilize the same egg naturally, there have been rare cases where more than one sperm manages to enter the egg due to fertility treatments resulting in polyspermy. this abnormal process would not result in a viable embryo.
What is a super twin baby?
A super twin baby is a term used to describe a set of twins that are born as part of a rare and unusual phenomenon known as superfetation. This happens when a woman ovulates while already pregnant, resulting in the conception of a second embryo.
Usually, during pregnancy, the woman’s body releases hormones that suppress further ovulation to prevent a second pregnancy. However, in some cases, the body fails to suppress ovulation, and a second fertilization occurs, resulting in twins that were conceived at different times.
When this happens, the twins may have different gestational ages, meaning that they can be born at different stages of development. The difference in gestational age can be anywhere from a few days to several weeks, making one twin significantly smaller and younger than the other.
Super twin babies are an incredibly rare phenomenon, and only a few cases have been reported worldwide. These cases require careful observation and monitoring as each twin may require different medical interventions and care due to the difference in gestational age.
While having super twin babies may be exciting for parents, it can also come with challenges, such as ensuring each twin receives the care and attention they need, and managing the different developmental milestones each may reach at different times.
Super twin babies are twins born as a result of a rare and unusual phenomenon called superfetation, where a woman ovulates while already pregnant. This results in twins with different gestational ages and requires careful monitoring and intervention for them to grow and develop healthily.