Can triplets have different DNA?
The study of 381 pairs of identical twins and two sets of identical triplets found that only 38 were genetically identical, Tina Hesman Saey reports for Science News. Most had just a few points of genetic mismatch, but 39 had more than 100 differences in their DNA.
Like twins, triplets and other higher-order multiples can be categorized by their zygosity or degree of genetic similarity. Though triplets are most commonly fraternal (dizygotic or trizygotic), it is possible for triplets to be identical (monozygotic).
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“Most experts put the odds of identical triplets at one in 200 million births,” Tiberius said. “I talked to a statistician and apparently the odds of a 45 year old having identical triplets are one in 20 billion.” It's quite rare to become pregnant without medical intervention at 45, according to Dr.
While all three sisters were determined to be 99 percent European, the individual breakdowns of different ethnicities varied among the sisters. Nicole Dahm's DNA was considered 11 percent French and German, though sister Erica's percentage of this ethnic blend was 22.3 percent.
The Times said the phenomenon of twins or triplets having different fathers can occur when a woman, having ovulated at least twice in the same cycle, sleeps with more than one man within 24 hours and conceives children by them.
Thus, early researchers quickly determined that the smallest combination of As, Cs, Gs, and Us that could encode all 20 amino acids in RNA would be a triplet (three-base) code. A triplet combination, or codon, would allow for 64 possible combinations (four bases at each of three positions = 4 × 4 × 4 = 64).
Preliminary evidence indicating that the genetic code was indeed a triplet code came from an experiment by Francis Crick and Sydney Brenner (1961). This experiment examined the effect of frameshift mutations on protein synthesis.
Since embryo splitting is a random spontaneous event that happens by chance, it doesn't run in families. Genes are not involved and there's no scientific evidence that being from a family with identical multiples has any impact on your odds of having twins. The same is not true for fraternal twins.
Though it's possible that it's a mistake, it's extremely unlikely. Relationship predictions are almost always accurate for people who are second cousins or closer.
Can siblings have different DNA?
Because of recombination, siblings only share about 50 percent of the same DNA, on average, Dennis says. So while biological siblings have the same family tree, their genetic code might be different in at least one of the areas looked at in a given test. That's true even for fraternal twins.
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However, a triplet code produces 64 (43 = 64) possible combinations, or codons. Thus, a triplet code introduces the problem of there being more than three times the number of codons than amino acids.
There are 64 possible nucleotide triplets (4 possible nucleotides in groups of three = 43), which is far more than the number of amino acids. Three of these codons are stop codons: UAA, UAG, and UGA.
They are identical because both siblings have the same set of DNA from mom and the same set of DNA from dad. Since both sets are the same they share 100% of their DNA. Fraternal twins are really just siblings who share the same womb. Each starts out as a separate egg fertilized by a separate sperm.
In fact, the National Forensic Science Technology Center states that, “no two people have ever been found to have the same fingerprints — including identical twins.” Also, it's important to keep in mind that fingerprints also vary between your own fingers — this means you have a unique print on each finger.