Are you raising a “jacket”?

DETERMINING the paternity of a child in Jamaica is not always left up to exact science. Many theories abound concerning parentage, based on physical characteristics like nose size, skin colour, hair type and even mannerisms — like the way one walks — that will be used to tell if a man is wearing a “jacket”.

It can be devastating for a man to hear that there are doubts about the children he allegedly sired, and many children have not been “owned” by their paternal families because other people make it their duty to point out stark differences.

But are traits like tongue rolling, cleft chin, blood type, ear lobe appearance, finger length, eye colour and hair colour enough to determine paternity in the absence of the litmus test — DNA?

While some people will swear by the belief that if the ears don’t match, the DNA won’t either, Dr Barry Starr, director of outreach activities in the department of genetics at Stanford University, says the only trait that would raise a red flag for him if they don’t match is blood type, and even that isn’t foolproof.

The blood typing standard holds that certain values must be true if a child is to be the child of two particular parents. For example, if a mother is type A and a child is A, the father can only be type A, B, AB or O; if mom is B and the child is B, dad can only be A, B, AB or O; if mom is AB and the child is AB, dad can only be A, B or AB; and if mom is O and the child is O, dad can only be A, B or O.

But even this, Dr Starr said, isn’t absolute.

“This is because nothing in genetics is absolute. All you have is what is more or less likely. [Even with] blood type there are plenty of exceptions. The most interesting case for me happened in Japan. An AB dad had a child with an O wife and had an AB child. This is impossible, according to straight up genetics. But this guy was the dad. What had happened was that his A and B alleles got stuck together. So he passed it on as a single AB. This also means he could have had an O child. In fact, AB parents having O children happens more often than you might think in certain Asian countries because of something called cis-AB. And people from India can have an O blood type and have an AB child more often than you might think because of the Bombay blood group,” he explained.

With regard to things like tongue rolling, cleft chin, earlobes and finger length, Dr Starr said these aren’t positive determinants at all.

“A study done way back when concluded that tongue rolling was a dominant trait (like brown eyes or not-red hair). What this would mean is that two parents who couldn’t roll their tongue could not have a tongue roller for a child. This is wrong. Further studies have shown that tongue rolling doesn’t really follow this pattern. For example, identical twins, who share all of the same DNA, can’t always both roll their tongues. So if you have a tongue rolling child and you can’t roll your tongue, this is not a cause for concern.”

As it relates to cleft chin, Dr Starr said this is a classic example of something called variable penetrance.

“What this phrase means is that sometimes someone can have the right gene but not have the trait. It might be that a lot of folks have a gene that shuts the cleft gene off. So they have an off copy that can get turned back on in a child. Or maybe something environmental can affect the trait — like sometimes injury in the womb can keep a child’s eyes blue even though the child has the genes for brown eyes, and so they could have a brown-eyed child themselves.”

The earlobes and finger length argument usually surrounds whether a parent with attached earlobes can have a child with unattached earlobes, and whether both parents with a ring finger longer than the index can have a child with the opposite.

“In fact, parents with attached earlobes can have a child with unattached earlobes. In fact, some people can have one of each earlobe…,” Dr Starr said.

“Of all these traits, the one that would concern me the most is [mismatched] blood type. Even though there are exceptions, they aren’t all that common.”

Dr Starr said we have two different copies of each of our genes — one from mom and one from dad, and each of these copies can come in different forms, called alleles. “This is why two people without red hair can have a redheaded child. Or why two parents with brown eyes can have a blue-eyed child. In each case, the parents have two different copies of a gene for the trait. The same sort of thing works for eye colour.

“Genetics is anything but black and white. It is all shades of grey,” he said.

But is there no actual physical trait that can help you tell?

Patrick L Wilson, licensed certified genetic counsellor and clinical assistant professor at the University of Oklahoma Health Sciences Centre, said two common conditions often used to determine paternity on solely physical traits are deafness and dwarfism. And then, even with those, there are exceptions.

“[For instance] two individuals are deaf — one is from a genetic mutation affecting hearing, the other from an infection that damaged the nerve. They have a child who can hear. Is the father someone else? Not necessarily. Both parents have the same physical feature/trait, but the cause for that trait was different. Then two parents are 2.2m tall. They have a child who is 1m tall with features of achondroplasia, a form of dwarfism. Achondroplasia is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. About 80 per cent of people with achondroplasia have average-size parents; these cases result from new mutations in the FGFR3 gene. In the remaining cases, people with achondroplasia have inherited an altered FGFR3 gene from one or two affected parents.”

He also warned against using conception dates in your determination of who is the father.

“Conception dates can be tricky because a woman’s cycle/menstrual period is not always the same. Stress, hormone levels and other things may influence the length of time between cycles. So this may not accurately determine who the possible father could be. Similarly, if the woman’s cycle dates are certain and she has an early labour/delivery, you have the same question. Did she have an infection, did she fall and go into labour, or did she have an affair two months prior to telling her husband she was pregnant?”

As it relates to changing the culture locally, Wilson maintained that while DNA testing will give you a yes/no answer, only education will solve the problem or perception.

“Just as people thought the earth was flat, after they were “properly educated” they realised that what they thought was correct was actually wrong. The earth is round, and they do not fall off a cliff at the edge of the sunset,” he said.