All expectant parents wonder who their new little one will look like. In fact, it’s a fun guessing game throughout pregnancy. Will he have my partner’s pointy nose? My musical gifts? Granddad’s red hair? And the list goes on…
But can you really tell what your baby will look like before he’s born?
Here are some clues to go by:
Dark and curly hair are both dominant genes. So if your partner has dark, curly hair and you have blonde, straight hair, your baby’s hair will tend more towards your partner’s side of the gene pool.
But hair colour is on a spectrum from light to dark, and there’s more than one gene involved in hair type and colour, so it’s not possible to predict the exact outcome. Even if both parents have dark hair, if there are recessive genes for light hair from ancestors, your baby might inherit those genes and have lighter hair.
Like hair colour, eye colour is polygenic. Human eye colour comes in a whole spectrum of colours, ranging from brown and hazel, to green and blue. Brown eyes are usually dominant. But just like hair colour, your baby may inherit recessive genes from grandparents and two brown-eyed adults may have a blue-eyed child.
Height and weight
It’s no surprise that genes play a big role in weight and height. Tall parents tend to have tall kids. Sr Merlyn Glass, a genetic counsellor of the National Health Laboratory Services, explains that because of their genetic make-up, every person has a tendency towards a particular body type, but that environmental factors and lifestyle choices play a significant role, too.
Intelligence is inherited, but it’s also the result of stimulation. A child who’s genetically blessed with a wonderful brain, but who’s not stimulated, talked to, read to or educated, won’t develop to his full potential. On the other hand, a child with an intellectual impairment or developmental delay may improve significantly if he’s stimulated appropriately, explains Sr Glass. So in this case, it’s not all about the genetics.
There are certainly genetic components to personality. But, as with intelligence, the combination of factors involved – upbringing, personal history and cultural input – is so complex that it’s very difficult to unravel what is genetic and what is environmental.
Recently, there have been reports of a ‘novelty-seeking gene’, which makes a person prone to risk-taking behaviour. Certain psychological conditions, including depression and a tendency to addiction, have also been shown to have a genetic element.
If you or your partner has crooked teeth, buck teeth, or a big gap between the front teeth, you might want to start saving for your child’s orthodontics. The size and configuration of the jaw, as well as the angle and alignment of the teeth, is genetically determined.
Sometimes, a child will inherit a combination of characteristics that results in problems with bite and alignment – like big teeth from mom’s side and a small jaw from dad’s side.
There are a host of odd little traits that are inherited and passed down through the generations. Here are a few:
- A cleft chin is hereditary. It’s caused by the lower jawbone not fusing totally during development. A dimple is a small fault in the cheek muscle. Both of these are dominant traits, says Sr Glass. If you or your partner has one of these traits, there’s a 50/50 chance your baby will inherit it. However, these traits are inherited with ‘variable expression’. This means that the cleft may be smaller, or the dimple may be in a different spot, or not appear at all until the next generation.
- When your baby is born, you may notice other little characteristics like his fingernails, toes or toenail shape and even fingerprint patterns. More unusual traits, such as webbed toes, can also be inherited.
- Left-handedness is genetically determined. You won’t be able to tell whether you child’s going to be left-handed until he’s about 18 months old. The left-handed gene is recessive. Two right-handed parents can have a left-handed child, but if you ask around the extended family, you’ll probably find that there are other lefties around.
- It has been shown that genes even influence our food preferences – particularly when it comes to vegetables. Broccoli and some others contain a substance that only some people can taste – and it’s bitter!
4 facts you need to know about your baby’s genetic make-up:
Sr Glass explains some of the facts that will help you understand your baby’s genetic make-up:
- Some of our inherited traits are inherited in a dominant way. Sr Glass explains that if one parent has this trait, there will be a 50/50 chance that the baby will have it.
- Some genes are recessive. A recessive trait will often be hidden, and not observable. Unless both parents pass their copy to the baby.
- Many human characteristics are polygenic, the result of a number of different genes that act together. Not only one single gene will determine eye colour, for instance.
- Many characteristics or conditions are multifactorial. This means that there’s a genetic component, but environmental factors also interact with the genes to result in a particular characteristic. So your child might have a genetic predisposition towards an allergic condition, but certain foods or environmental conditions will trigger the symptoms. Studies of genetically identical twins show that nutrition, for example, plays a significant role in many aspects of development, including weight, height and intelligence.
- Genetic counselling is available at Charlotte Maxeke, Chris Hani Baragwanath Rahima Moosa Mother and Child Hospitals, as well as the Donald Gordon Medical Centre.
- Noelene Kinsley’s a genetic counsellor in private practice in Johannesburg. Contact her on 082 547 5720, or 011 678 5969.
- A clinical genetic service and counselling are available at the University of Cape Town. Contact 021 406 6698/6995.
- Stellenbosch University has a clinic at Tygerberg Hospital. Contact 021 938 9807, or email firstname.lastname@example.org.
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