Identical twins will always have the same blood type because they were created from the same fertilized egg (fraternal twins can have different blood types — again, providing the parents do — because they are created by two fertilized eggs).
So how could identical twins end up with different blood types? The answer is that DNA is not set in stone. DNA can and does occasionally change (or mutate). If that DNA change happened in the exact right spot, then it could very well affect blood type.
Identical twins are also known as monozygotic twins and are the result of a single fertilized egg which splits into two after conception. Identical twins share the same genetic profile including the same sex and blood type.
Twin blood group chimerism seems to be very rare in humans. The 30-40 previously reported cases usually were found by mere coincidence during routine blood grouping in hospitals or blood banks. Usually in these cases frank blood group mixtures of, for example, 50/50%, 25/75%, or 5/95% at most were seen.
The quick answer to this question is that, in a twin pregnancy, it is the mother's genes that determine twins. First up, giving birth to identical twins is not genetic, but conceiving fraternal twins is. The mother may have the genetic trait of releasing two eggs in one menstrual cycle.
Identical twins have 100% of their DNA the same while fraternal twins share only 50%. But what about semi-identical twins? Well, they have 75% of their DNA the same.
Older women generally have a higher chance of conceiving twins. A 35 year old woman is about 4 times more likely to have fraternal twins than a 15 year old! That is because they are experiencing some hormonal changes as they near menopause. This could encourage their body to release more than one egg during ovulation.
Everyone has the same chance of having identical twins: about 1 in 250. Identical twins do not run in families. But there are some factors that make having non-identical twins more likely: non-identical twins are more common in some ethnic groups, with the highest rate among Nigerians and the lowest among Japanese.
But there are many other, less common, twin subtypes. These include conjoined twins, superfetation, heteropaternal superfecundation, polar body twins, semi-identical twins, and mirror-image twins.
Brothers and sisters don't always share the same blood type. The genotype of both parents plays a role in defining the blood type. For instance, children of parents with the genotypes AO and BO may have the blood types A, B, AB, or O. Thus, siblings do not necessarily have the same blood type.
Longer lives
When analyzing the data by gender, the researchers found that female identical twins lived, on average, about 63.4 years, whereas female fraternal twins lived about 61.4 years and the general Danish female population lived about 58.8 years, Sharrow said.
Identical (i.e., monozygotic, or MZ) twins share 100 percent of their genes, whereas fraternal (i.e., dizygotic, or DZ) twins generally share only 50 percent of their genes.
Identical twins share the same genomes and are always of the same sex. In contrast, fraternal (dizygotic) twins result from the fertilization of two separate eggs with two different sperm during the same pregnancy. They share half of their genomes, just like any other siblings.
While many people can't tell them apart, Mary-Kate and Ashley are not identical, but rather fraternal: Mary-Kate is one inch taller than her sister and is left-handed, while Ashley is right-handed.
In 99.9% of cases boy/girl twins are non-identical. However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair.
The blood type of a child is determined by both of the parents. Each parent donates an allele for the ABO blood group. The A and B blood alleles are dominant while the O is recessive, meaning that the O will not be expressed when dominant genes are present.
It's a common misconception that twins skip a generation in families. There is absolutely no evidence, other than circumstantial, that twins are more likely to occur every other generation.
Twins share the same genes but their environments become more different as they age. This unique aspect of twins makes them an excellent model for understanding how genes and the environment contribute to certain traits, especially complex behaviors and diseases.
Mixed-gender twins are the most common type of fraternals, some 50 percent are boy-girl.
Twins not only have a bestie from birth — they also live longer than singletons. And those two factors may be related, according to new University of Washington research.
In 2021, according to the Australian Bureau of Statistics (latest report as of October 2021) there were 4,248 multiple births representing 1.5% of all births (309,996) in Australia. This comprised 4,185 pairs of twins and 63 sets of triplets and higher order multiples.
Many people believe twins skip a generation, but that's just a myth. The idea that twins skip generations likely comes from the fact that the genetic factors contributing to twins only come from the gestational parent's side.
However, few genes appear to be definitively linked to hyperovulation, so it could just be that genetics in general on the mother's side contribute to the probability of having fraternal twins. Heredity on the father's side, on the other hand, does not increase a couple's odds of having twins.
With twin pregnancies, both the pregnant person and twins face a higher risk of complications. Prenatal checkups occur more frequently with twin pregnancies, making it possible to detect issues in earlier stages. Twin pregnancies are high risk because there are many potential complications.
They come from the same fertilized egg and share the same genetic blueprint. To a standard DNA test, they are indistinguishable. But any forensics expert will tell you that there is at least one surefire way to tell them apart: identical twins do not have matching fingerprints.