I am sure most parents will know that the human race begins with the egg and sperm. The egg contains information coded in DNA from the mother as well as a functioning cell with battery and starter pack to kick start reproduction. The much smaller sperm contains information coded in DNA from the father as well as a whippy tail to get it swimming to deliver the information to the egg.

What is important is the genetic information coded in the DNA contained in egg and sperm. This is the basis of biological relatedness. What is this information and where does it come from? Your DNA (deoxyribonucleic acid) is basically the instruction manual of how to make you. Every single cell in your body: your liver cell, your blood cell, your skin cell contains a full set of your DNA. The only cells that do not contain a full set of instructions (DNA) are the egg and sperm. They each only contain half. Busy in the germ lines of female ovaries and male testes are the egg and sperm factories. Here, the DNA dances about a bit, and gets chopped in half at random and packaged up into eggs in the ovary and sperm in the testes. It is at conception that the sperm meets egg story finishes and as in the Spice Girls song, “two become one” literally. A novel instruction manual is made for the new individual based on information from father and mother.

So what does this have to do with parenting? Well, whilst environment and upbringing has significant impact on how someone turns out, there is no denying the existence of genetic effects. It doesn’t take a clever-clogs to work out that identical twins (who share 100% DNA and the same womb at the same time (scientifically referred to as gestational environment)) are a lot more similar than non-identical twins (who share gestational environment but only 50% of DNA), for a start, non-identical twins can be different genders! Their genetic relatedness to each other is no different from any other brother or sister. It is consistently backed up in scientific literature involving twin and adoption research over a range of disorders (learning difficulty, ADHD, schizophrenia, depression, anxiety, autism as well as physical conditions), that monozygotic (identical) twins are more similar to each other than di-zygotic twins (non-identical). This is true even if the twins are raised apart, thereby disentangling the tendency of society to treat identical twins more similarly. This is good evidence for genetic effects and no one really bothers to argue this anymore.

Where debate continues, is on the matter of more or less of environment or genetics, but I am quite happy to fence sit at 50% of each. In reality, research is moving towards relative percentages differing from person to person with nature and nurture interacting in a multitude of ways making the simplistic nature versus nurture argument completely obsolete. The percentages don’t matter, what matters is that genes are an important contributor and it is a contributor that we have knowledge and control over. When “control over genes” is mentioned people automatically think about eugenics, gene therapy, genetic engineering and designer babies, which is expensive, not widely available and ethically controversial. They tend to ignore the easiest and most widely used method of gene selection.

Genetics has merely given evidence to what people already knew: that “the apple doesn’t fall far from the tree”. For time immemorial dog and horse breeders have been selectively mating animals to produce favourable traits in their progeny; long before IVF and the debate on designer babies. In humans the basis of attraction has evolved to envelope the physical traits of health and success (tall height, glowing skin, good musculature) and Eastern and Western societies alike have chosen suitors based on family background to promote the likelihood of healthy and successful succession based on past record of ‘genetic’ performance (what their family is like). These days there is more emphasis on personality and intelligence than health and virility, but the same still holds true. If you don’t like the personality or intelligence level of your partner and can’t stand any members of his/ her family, there is a good chance that you might not ‘like’ your child. This will be truer still if you also do not like yourself or any members of your own family!

This might sound un-PC, unromantic and overly pragmatic, but with my behavioural geneticist hat on, a major step in helping parenting is finding the right spouse. Not only to love and support you throughout your life, but also to provide children with easy temperament and a personality that won’t jar with yours! This is important as unlike a lover or a partner, who you can divorce and be rid of (society and religion permitting), your children are yours and your responsibility until they are 18 years old at least, whether you like it or not!

Thankfully it is not as hard as it sounds to find compatible stock, because presumably most people seek to find partners that they actually like as well as love. The “like” part is important here as whereas a good dose of physical attraction, athleticism, sexual prowess and general lusty desirability can save any marriage, these traits are no good in helping you “like” your child, and if it does, then you probably need professional help as incest is illegal in most countries. If you would enjoy 18 years of your own or your partner’s non-sexual company, then you have at least the best chance in genetic terms of liking your children. For women, given that conception is now available by IVF from sperm donation, it is interesting to consider whether one would select the same profile for a sperm donor (thus providing you with children of biological relatedness) as one would consider for a spouse (sperm donor plus husband and father). An aggressive, dominating, powerful alpha-male type might be an exciting conquest and offer physical protection as a partner, but an aggressive, dominating five year old son? That’s a recipe for grey hair! Personally, for me, whilst there would be a broad overlap in the husband/ son characteristics wish-list, the two would be slightly different. Whilst a husband who called his mother every day and wanted to visit his mother weekly would be abhorrent as a husband, this would sound like a pretty cool son!

During my training, I helped conduct genetic counselling assessments for couples where there was a history of autism in the family. Autism is a disorder of social interaction and communication with a likely genetic basis, the common form is thought to be a polygenic disorder, whereby risk is conferred by multiple as-yet-unidentified genes. Most heritable traits, such as intelligence, aggression and attention are also likely to be due to multiple genes in combination. The genetic counselling assessment involves taking an extremely thorough family history for symptoms of autism and its broader spectrum, going back through as many generations as there is information. The way it works is that the more “genetic loading” there is in the family (i.e. the more family members with the disorder or traits), and the closer they are in relation to the parents, (i.e. the greater likelihood of shared genetic material), the greater the statistical probability that the couple in question will have a child with autism. Parents and siblings share 50% of genes with any one child. Grandparents, aunts, uncles, half-siblings share 25% genes, great-grandparents and cousins share 12.5% genes and so on. This family history is important as a person can be unaffected but still carry risk genes for a particular trait or disorder if they have high “genetic loading”. If you extrapolate this to other potentially genetically determined traits, you can see the importance of assessing your spouses’ family in determining outcome for your children. If your partner is the most wonderful person but he has the most annoying brother who you can’t stand, there is a possibility that your child will inherit this “annoying” gene that was being carried but not expressed in your partner. In order to limit the likelihood that your child will be genetically “annoying”, then neither you nor your spouse or any member of your families should be annoying. Of course, they can still develop propensity to be annoying via environmental factors! Sometimes two exceptionally bright parents produce offspring of average intelligence leading to confusion and disappointment, when in actuality looking at the broader family; it may be easy to tell that the parents themselves were exceptions to the prevalent genetic loading.

For me, I was lucky in that the man I fell in love with and subsequently chose to marry and be the father of my children is a sociable and intelligent man with easy temperament, low aggression and blind optimism. Although it is often infuriating (he has a penchant to leave windows open when going out because the chance of burglary in London is low in his mind set), what I have gained from his DNA is a daughter who is relaxed and easy going. On breaking her left leg, after the initial pain had settled, she never complained or moaned once and would cheerfully state “Well, my right leg is O.K”! An older colleague of mine stated that she could never hate her ex-husband despite his affair and the breakdown of their marriage as his genes gave her two wonderful, intelligent and compassionate children.

Genetic consideration should also be given to ground expectation of your children’s ability.  It’s unlikely that you can ‘inherit’ ability for needlepoint. What is heritable is “visual acuity”, “fine motor skills”, “ability to concentrate and pay attention to detail”, “low sensation seeking”; traits which would make it possible given environmental exposure, passion and encouragement to excel at needlepoint. If neither you, any member of your family or your partner and his family have anyone with any of these core abilities, your dreams for spawning the next “World Needlepoint Champion” aren’t impossible, but the odds are stacked against you as genetically, you would be banking on a genetic mutation to deliver the goods. Environmentally, you can still make good headway and environment can definitely conquer much of genetic disadvantage, but could it conquer others with genetic and environmental advantage? Unlikely. Whilst I don’t believe in ruling out potential in children, I have enough clinical experience to see that unrealistic expectations are really corrosive to the child’s self-esteem. Parents who have overly aided and abetted their children into academically competitive schools only to confront the child prematurely with the limitations of their ability and press the self-destruct button, children with learning difficulties made to remain in mainstream school to struggle academically and socially as parents are unwilling to face up to reality and accept their children for who they are. Knowledge about genetic background can help as fore-warned is fore-armed. What, if any, action is to be taken is up to the individual to decide, and family histories and traits are merely a very rough guide rather than an oracle.

Different people will respond differently. In the genetic counselling for autism clinic, when we relayed the statistical probabilities of having a child affected by autism back to families, the disparity in reactions was great. Despite relaying the same low statistical probability (less than 5%) back to two couples with similar genetic loading, one felt happy to ignore the very low level risk, but in the other, the woman decided to divorce her husband (where the family history lay) rather than procreate with him and run any risk of having a child with autism.

In my case, I warned my husband from the outset that should he be hoping for a brood of NBA contenders or 100m sprinters then he had better think again about his choice of wife; height and fast twitch muscle fibres being rather lacking in my family. In his turn, I was to wipe singing in tune from my list of aspirations for our children. I think together we might have an unstoppable force for card games and scrabble.