Children from identical parents are genetic siblings

Studies have revealed that children from identical twin sisters who married identical twin brothers will all be genetic siblings who share about 50 percent of their DNA.

Geneticists explained that all of the two couples’ children would be genetic siblings, sharing 50 percent of their genes with their brothers, sisters and first cousins, except for twins, whose DNA sequences are a perfect 100 percent match.

According to the study, humans have around 30,000 genes with two copies of each of those genes in every chromosome and its corresponding copies varying slightly from one another.

Chromosome is a thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

In the human body, each cell contains 23 pairs of chromosomes, with matching genes.
Each gene copy comes in the same size and shape and sits in the same position on the chromosome. The two pairs will contain the same information, but in a different order.

This means that; except for sex cells, Sperm and egg cells contain just one copy of every chromosome, which is essentially a mash up of the pair, that when a sperm fertilizes an egg they make an embryo that has the correct number of genes and chromosomes.

Meanwhile, the embryo will have one copy of each gene from the mother and one from the father, combined into a new set of 23 chromosomes.

Geneticists said twins have perfectly matched DNA that offers a rare opportunity to rule out which traits are behavioral.

According to them, the rate of all twin births – both fraternal and identical – has risen dramatically since the 1980s, mostly due to the fact that women are having children later in life and getting IVF treatments.

Twins account for about three in every 1,000 births and in 1980, 19 out of every 1,000 births was a pair of twins, while in 2016; every 33 out of 1,000 births resulted in twins.

Africa is home to the world’s highest rate of twin-births among regions in the developing world, with about 18 sets of twins per 1000 births

A Demographic and Health Surveys of 75 developing countries collected between 1987 and 2010 revealed that Nigeria had a rate of 19 sets of twins per 1,000 births.

According to a co-director of the Michigan State University Twin Registry, Dr Alexandra Burt, within the first two weeks of a pregnancy, a single [fertilized egg] divides, as both implant and become two people.

‘That means that each child will share as many genes with their aunt as they will with their mother. The children are cousins “in real life” but, in terms of their DNA, they are siblings.’

The male halves of each couple don’t share DNA with the female halves, so each pair can safely reproduce.

Though they will be legal cousins, children of the separate couples will share roughly 50 percent of their DNA, like siblings, Burt said
Burt explained that there are any genetic health risks to being the child of two identical twins, adding that the respective children of one set of twins – whose other parents are not twins – will still be genetic half siblings, sharing as many genes as, if they had one parent in common.

“No matter how much DNA they share, children who grow up with the same set of parents will be shaped differently by that experience from their cousins growing up with a different – if genetically identical – set of parents,” she added.

The study which was carried out on the identical twin sisters Brittany and Briana Deane, who married identical twin brothers Josh and Jeremy Salyers in Twinsburg, Ohio, showed that, while there are plenty of studies on the offspring of identical twins, there aren’t enough children of two pairs of identical twins to predict much of what the two sets of Salyer kids might be like.

“Such children are even rarer than their already rare parents, and how their lives pan out will be of great interest to geneticists,” she noted.

She continued: ‘They are clones of each other, created by nature, and you have got a case of two of these magical sets of human beings meeting and falling in love.

“If it didn’t happen in real life, you wouldn’t believe it could happen and you couldn’t write a better story than that.”