Frequently Asked Questions-
1. Will these children be identical twins as well, even if they are cousins?
These children will not be identical twins because identical twins are formed when the zygote growing in a mother’s uterus separates and the two new unborn babies share placenta. So, if they are cousins there is no way that the children can be identical twins because they did not originate from the same egg in the mother’s womb. None of the children can be “identical twins” unless they are born that way. If one mother of a child has twins and it is mentioned that the two are identical, then that is the only way the siblings can be identical twins. If the sister to the mother also has identical twins, just each set of twins are identical. Even though each mother had identical twins, both sets of twins are not identical to the other set, they are only identical to their one twin. Like said, even though the parents each have the same genetic make-up (because they were identical, meaning they started as one zygote then split into two unborn babies), their children might not have the same genetic make-up as one another, unless, of course, they are identical twins. Like expressed in Mendelian Genetics, to predict the outcome of your baby, Punnett Squares are used. Using the Punnett Squares, you can see that even with identical twins, there is a different probability of what each child will look like depending on the genes. Even though this is true for each child and set of parents, what is unique about identical twins marrying and having a child is that they will have the same probability of outcomes with each child. Although they have the same probability, because it is not certain what the child will look like, the children will all look different; similar, but not exactly the same. Legally, these children would be cousins, but genetically these children would be actual siblings.
2. Will these children look alike and have no individual or unique characteristics?
Although the children are different kids, they most likely will look oddly similar. This is because both of their parents have the exact same gene make-up as their sibling. This is not saying that the children will not have any unique characteristics because other factors than genetic make-up plays in a child’s actions and behavior. Environmental effects change the child and makes him/her more unique. For instance, a child that grows up in the south typically has a “southern” accent that is usually more slurred and is slower than people up north. A child raised in the northern part of the United States typically speak faster and have a more monotone kind of voice. Environmental effects of a child are not limited to just the way they speak, but many other things as well. The children are not growing up in the same household, therefore causes each individual child to act differently and in a distinct manner. Specific environmental characteristics of the uterus in which a fertilized egg is implanted and the health of the mother can have major impacts on the phenotype of the future child. In addition, accidents, poor nutrition, and other environmental influences throughout life can alter an individual's phenotype for many traits even if they are identical twins. Some genes are affected when certain factors are present in the environment. The triggering of genetically inherited diabetes by obesity or severe emotional stress is an example. Twins could carry the same genes for diabetes and depending on their lifestyles, one may develop it when one may not. If there are any differences in the phenotypes of identical twins, the environment is virtually always responsible.
These children will not be identical twins because identical twins are formed when the zygote growing in a mother’s uterus separates and the two new unborn babies share placenta. So, if they are cousins there is no way that the children can be identical twins because they did not originate from the same egg in the mother’s womb. None of the children can be “identical twins” unless they are born that way. If one mother of a child has twins and it is mentioned that the two are identical, then that is the only way the siblings can be identical twins. If the sister to the mother also has identical twins, just each set of twins are identical. Even though each mother had identical twins, both sets of twins are not identical to the other set, they are only identical to their one twin. Like said, even though the parents each have the same genetic make-up (because they were identical, meaning they started as one zygote then split into two unborn babies), their children might not have the same genetic make-up as one another, unless, of course, they are identical twins. Like expressed in Mendelian Genetics, to predict the outcome of your baby, Punnett Squares are used. Using the Punnett Squares, you can see that even with identical twins, there is a different probability of what each child will look like depending on the genes. Even though this is true for each child and set of parents, what is unique about identical twins marrying and having a child is that they will have the same probability of outcomes with each child. Although they have the same probability, because it is not certain what the child will look like, the children will all look different; similar, but not exactly the same. Legally, these children would be cousins, but genetically these children would be actual siblings.
2. Will these children look alike and have no individual or unique characteristics?
Although the children are different kids, they most likely will look oddly similar. This is because both of their parents have the exact same gene make-up as their sibling. This is not saying that the children will not have any unique characteristics because other factors than genetic make-up plays in a child’s actions and behavior. Environmental effects change the child and makes him/her more unique. For instance, a child that grows up in the south typically has a “southern” accent that is usually more slurred and is slower than people up north. A child raised in the northern part of the United States typically speak faster and have a more monotone kind of voice. Environmental effects of a child are not limited to just the way they speak, but many other things as well. The children are not growing up in the same household, therefore causes each individual child to act differently and in a distinct manner. Specific environmental characteristics of the uterus in which a fertilized egg is implanted and the health of the mother can have major impacts on the phenotype of the future child. In addition, accidents, poor nutrition, and other environmental influences throughout life can alter an individual's phenotype for many traits even if they are identical twins. Some genes are affected when certain factors are present in the environment. The triggering of genetically inherited diabetes by obesity or severe emotional stress is an example. Twins could carry the same genes for diabetes and depending on their lifestyles, one may develop it when one may not. If there are any differences in the phenotypes of identical twins, the environment is virtually always responsible.
Referring to the twins on the right, you can see that for example, the girl on the left has eyes that are closer together than her sister, and the girl on the right has a more oval-shaped head than her sister. These girls are identical twins, meaning they are stereotypically the same. However this may seem the case, it is untrue. Different things characterize a person and just because two people may seem like they are the same, they are not exactly the same; no two people are exactly identical.
3. How will this affect the twins' situation? Referring to Mendel’s Law of Segregation, the twins having children might be affected in several ways. Surprisingly, even though the twins each have the exact same DNA which would technically make their children siblings, the kids would not look exactly alike as their cousins. In Mendel’s Principle of Separation, it says that the various alleles that are responsible for a certain trait split up and separate until fertilization of an egg and a sperm. Therefore, unless the parents were purebred in every single genotype of a trait, the kids would each have a possibility of looking different because of the recessive genes. Aside from the obvious gene parts of this, environmental factors play a major role in how a child’s traits are. Even though each parent grew up in the same household as their sibling, there are distinct, unique characteristics about each person. This will influence the way their children behave and how they look. For example, if one family moves away from the same area they grew up in, the two families have a higher chance in being different than one another because of two different settings they live in. No two people are exactly alike, even if they are twins. This is because different things affect people and how they are emotionally, physically, and mentally.
In the University of Western Ontario, new research has been conducted, analyzing the differences between identical twins. Shiva Singh, a Molecular geneticist has been working with Dr. Richard O’Reilly, a psychiatrist to see if identical twins or monozygotic twins are the exact same genetically. Using the common disease, schizophrenia, the two used a pair of identical and monozygotic twins, one with the disease, and the other without it, to see if the other would develop it overtime as well. Before this research, it was believed that if one twin developed the disease, the other would have a 100% chance of developing it too. However, this is not the case. If one twin does develop the disease, the other just has a 50% chance of developing the disease as well, proving that in monozygotic twins, their genetic makeup is not identical, or the disease involves non-genetic effects. Concluding, that the twins are not the exact same person. This would make the children not exactly alike either. Their parents are not the same, so neither would each new family member, just like every ordinary family. The difference between any average family and these two families is that the cousins will look remarkably similar, yet not identical.
Now, looking at Mendel’s Law of Individual Assortment, you can infer that the twins might also be affected. This Law of Independent Assortment helps explain as to why there is a possibility that the children of each family will not look exactly alike. In this law, Mendel concluded that each individual allele for a trait independently create a pair for trait at fertilization, just like in the Law of Separation. Referring to meiosis, a type of cell division, the parent genotypes each split and then came together, creating a “mixture” of each parent’s genotype. This law created an explanation of how there such a diversity in the genotype of the offspring compared to the genotype of the parent. Each offspring inherits a dominant and recessive gene from the parent. Although a gene may be recessive, there is still a possibility that the child may have a phenotype of that recessive gene, depending on what kind of genotype the other parent has. This will allow each child each family has to possibly look different because of the recessive genes that play a part in the child’s genotype. Using the example shown in the video, each mother has blonde hair, a recessive gene. For this particular example, we will use “bb” to explain their genotype. Also in this example, each father had brown hair, a dominant gene. For this example, we will use “BB or Bb” to explain their genotype. Referring to the first example to the right, we can see that in each child’s genotype, both of the parents’ genotypes are involved in it. Although, the brown hair is shown as the phenotype because it is the dominant gene. Now, referring to the example to the left, we can see that each child inherits a mixture of both parents’ genotypes. Although they are not all identically the same, like the first example, each genotype is still a mixture of each parent genotype to make different possibilities.
Finally, referring to the last of Mendel’s laws, the Law of Dominance, the twins will also be affected here. The Law of Dominance will affect how the children look because of the dominant and recessive traits that are handed down from generation to generation. Each parent has the same genotype for each trait as their sibling and each of those traits has their own dominant features. This causes the children to have a higher chance of inheriting the dominant genes more than the recessive genes which will cause the children to look alike, even though they are cousins. There is a small possibility that some of the cousins will inherit the recessive genes that each parent carries around, but that is a small chance because the dominant trait typically blocks out the recessive one. Even though the children will look similar, they will not look exactly the same because of the possibility of this. The laws all have an effect on the children and how they look. With the Law of Dominance, it is expected that the children will most likely all look the same, or close to it, because the dominant trait overpowers the recessive trait(s). However, referring to the Laws of Independent Assortment and Segregation, we can see that there is still a possibility that the children will have different features. Also, referring to the Punnett Squares, we can see that for each trait, the genes that make up those particular traits can breed together to make a genotype that is different than each other sibling. After all, the twins' situation is just like every other family's, but there are two families with the same percentages with each possible trait. Even though there is a possibility of the children looking different, most likely the children will have all the same, or close to the same characteristics because of the dominant genes that run in the family.
The twins should not not have any problem with their children having defects. They could give their children a sexually transmitted disease, though. Also, the RH of the blood could have a problem. If the Rh of the mother’s fetus is positive or negative and then the father’s is negative then there could be a fatal defection in the child. Back in the day, this was a major concern but now they have created a serum that can neutralize the problem. So, the percentage of the defects was thirteen percent, but with the medicine it was knocked down to one percentile. The blood of the parents, all in all, do not have any more effect on the children compared to a child whose parents were not identical twins. In other words, the children have no change in their possibility of having any complications with blood. They are just like any other child.
Another important factor to remember about these twins is that even though they are each sets of identical twins, there is no increase in their chances of having twins as well. Technically speaking, the only real chance of an increase of a person having twins compared to another person is when a couple has fraternal (dizygotic) twins. This is because two eggs actually come down the fallopian tubes and are each fertilized. Identical twins occur when there is only one fertilized egg (like a normal pregnancy), but the egg splits into two. The fraternal twin chances are passed down from generation to generation, but not identical twins. It can be coincidental that you and someone in your family both have identical twins, but technically speaking, there is only a real change in the probability of having twins when you are dealing with the probability of having fraternal twins.
There are many different exceptions to the simple inheritance principles of genetics that we learned from Mendel. Because of these Exceptions to Simple Inheritance, it would make it very difficult for any offspring of twins who married twins to be identical. These cousins could definitely resemble each other as siblings would, but there are too many opportunities for differences to occur before and after being born. Polygenic traits are appearance traits like height and skin color but are influenced by multiple genes so these appearance characteristics will land on a spectrum making it hard to be identical. Intermediate Expression, Codominance, and Multiple-Allele Series genes all involve combinations of varieties of genes that affect things like blood type or voice pitch. Modifying genes and Regulator genes both alter or block how other genes are expressed in and individual. Incomplete Penetrance is when the environment alters a gene by triggering diabetes for example.
In addition to the Exceptions to Simple Inheritance, there are also Sex Related Genetic Effects that can alter how a gene appears depending on a person’s gender. Sex-Limited genes are inherited by both genders, but usually only appear in male or female, facial hair is an example. Sex-Controlled genes are expressed in both sexes differently. Genomic Imprinting is when a gene has a different effect depending on the parent who passed on the gene. Pleiotropy is when a single gene is responsible for a variety of traits, making it that much harder for the children of twins to resemble each other identically. In addition, Stuttering Alleles are defective genes that pass on conditions that get worse in each generation. The biggest influence of changes to the phenotype of twins or offspring of twins are environmental influences. Environmental influences can affect a mother while carrying a child, which could alter the physical characteristics of the baby. Also, environmental conditions and living in certain areas of the world can affect an individual’s phenotype throughout life. If there are any differences in the phenotypes of identical twins, the environment is often responsible. There are so many opportunities for differences to occur in genetics, it is surprising that anyone could look like anyone else.
In the University of Western Ontario, new research has been conducted, analyzing the differences between identical twins. Shiva Singh, a Molecular geneticist has been working with Dr. Richard O’Reilly, a psychiatrist to see if identical twins or monozygotic twins are the exact same genetically. Using the common disease, schizophrenia, the two used a pair of identical and monozygotic twins, one with the disease, and the other without it, to see if the other would develop it overtime as well. Before this research, it was believed that if one twin developed the disease, the other would have a 100% chance of developing it too. However, this is not the case. If one twin does develop the disease, the other just has a 50% chance of developing the disease as well, proving that in monozygotic twins, their genetic makeup is not identical, or the disease involves non-genetic effects. Concluding, that the twins are not the exact same person. This would make the children not exactly alike either. Their parents are not the same, so neither would each new family member, just like every ordinary family. The difference between any average family and these two families is that the cousins will look remarkably similar, yet not identical.
Now, looking at Mendel’s Law of Individual Assortment, you can infer that the twins might also be affected. This Law of Independent Assortment helps explain as to why there is a possibility that the children of each family will not look exactly alike. In this law, Mendel concluded that each individual allele for a trait independently create a pair for trait at fertilization, just like in the Law of Separation. Referring to meiosis, a type of cell division, the parent genotypes each split and then came together, creating a “mixture” of each parent’s genotype. This law created an explanation of how there such a diversity in the genotype of the offspring compared to the genotype of the parent. Each offspring inherits a dominant and recessive gene from the parent. Although a gene may be recessive, there is still a possibility that the child may have a phenotype of that recessive gene, depending on what kind of genotype the other parent has. This will allow each child each family has to possibly look different because of the recessive genes that play a part in the child’s genotype. Using the example shown in the video, each mother has blonde hair, a recessive gene. For this particular example, we will use “bb” to explain their genotype. Also in this example, each father had brown hair, a dominant gene. For this example, we will use “BB or Bb” to explain their genotype. Referring to the first example to the right, we can see that in each child’s genotype, both of the parents’ genotypes are involved in it. Although, the brown hair is shown as the phenotype because it is the dominant gene. Now, referring to the example to the left, we can see that each child inherits a mixture of both parents’ genotypes. Although they are not all identically the same, like the first example, each genotype is still a mixture of each parent genotype to make different possibilities.
Finally, referring to the last of Mendel’s laws, the Law of Dominance, the twins will also be affected here. The Law of Dominance will affect how the children look because of the dominant and recessive traits that are handed down from generation to generation. Each parent has the same genotype for each trait as their sibling and each of those traits has their own dominant features. This causes the children to have a higher chance of inheriting the dominant genes more than the recessive genes which will cause the children to look alike, even though they are cousins. There is a small possibility that some of the cousins will inherit the recessive genes that each parent carries around, but that is a small chance because the dominant trait typically blocks out the recessive one. Even though the children will look similar, they will not look exactly the same because of the possibility of this. The laws all have an effect on the children and how they look. With the Law of Dominance, it is expected that the children will most likely all look the same, or close to it, because the dominant trait overpowers the recessive trait(s). However, referring to the Laws of Independent Assortment and Segregation, we can see that there is still a possibility that the children will have different features. Also, referring to the Punnett Squares, we can see that for each trait, the genes that make up those particular traits can breed together to make a genotype that is different than each other sibling. After all, the twins' situation is just like every other family's, but there are two families with the same percentages with each possible trait. Even though there is a possibility of the children looking different, most likely the children will have all the same, or close to the same characteristics because of the dominant genes that run in the family.
The twins should not not have any problem with their children having defects. They could give their children a sexually transmitted disease, though. Also, the RH of the blood could have a problem. If the Rh of the mother’s fetus is positive or negative and then the father’s is negative then there could be a fatal defection in the child. Back in the day, this was a major concern but now they have created a serum that can neutralize the problem. So, the percentage of the defects was thirteen percent, but with the medicine it was knocked down to one percentile. The blood of the parents, all in all, do not have any more effect on the children compared to a child whose parents were not identical twins. In other words, the children have no change in their possibility of having any complications with blood. They are just like any other child.
Another important factor to remember about these twins is that even though they are each sets of identical twins, there is no increase in their chances of having twins as well. Technically speaking, the only real chance of an increase of a person having twins compared to another person is when a couple has fraternal (dizygotic) twins. This is because two eggs actually come down the fallopian tubes and are each fertilized. Identical twins occur when there is only one fertilized egg (like a normal pregnancy), but the egg splits into two. The fraternal twin chances are passed down from generation to generation, but not identical twins. It can be coincidental that you and someone in your family both have identical twins, but technically speaking, there is only a real change in the probability of having twins when you are dealing with the probability of having fraternal twins.
There are many different exceptions to the simple inheritance principles of genetics that we learned from Mendel. Because of these Exceptions to Simple Inheritance, it would make it very difficult for any offspring of twins who married twins to be identical. These cousins could definitely resemble each other as siblings would, but there are too many opportunities for differences to occur before and after being born. Polygenic traits are appearance traits like height and skin color but are influenced by multiple genes so these appearance characteristics will land on a spectrum making it hard to be identical. Intermediate Expression, Codominance, and Multiple-Allele Series genes all involve combinations of varieties of genes that affect things like blood type or voice pitch. Modifying genes and Regulator genes both alter or block how other genes are expressed in and individual. Incomplete Penetrance is when the environment alters a gene by triggering diabetes for example.
In addition to the Exceptions to Simple Inheritance, there are also Sex Related Genetic Effects that can alter how a gene appears depending on a person’s gender. Sex-Limited genes are inherited by both genders, but usually only appear in male or female, facial hair is an example. Sex-Controlled genes are expressed in both sexes differently. Genomic Imprinting is when a gene has a different effect depending on the parent who passed on the gene. Pleiotropy is when a single gene is responsible for a variety of traits, making it that much harder for the children of twins to resemble each other identically. In addition, Stuttering Alleles are defective genes that pass on conditions that get worse in each generation. The biggest influence of changes to the phenotype of twins or offspring of twins are environmental influences. Environmental influences can affect a mother while carrying a child, which could alter the physical characteristics of the baby. Also, environmental conditions and living in certain areas of the world can affect an individual’s phenotype throughout life. If there are any differences in the phenotypes of identical twins, the environment is often responsible. There are so many opportunities for differences to occur in genetics, it is surprising that anyone could look like anyone else.