It isn’t always straightforward: parents who both have blue eyes can still produce babies with brown or green eyes, since many genes are required to make the black and yellow pigments needed for darker eyes. For a recessive gene to appear you need two copies—one from each parent, otherwise it will skip generations until it meets a match.
To complicate matters further, not all traits are decided by one gene. Tongue rolling and freckles, for example, are decided by a single gene, but other traits such as skin color, height, and body mass are thought to be contributed to by a number of different genes. Research into the field of genetics is ongoing, particularly in medical history.
Identical twins share 100 percent of their genes. Fraternal siblings share 50 percent of their genes.
In many of these cases, however, there is also some interplay with the environment that can affect these built-in blueprints. As diet improves in each country, so heights increase among the population.
In the same way, what is written in your baby’s genes is only half the story—there may be many lifestyle and external influences that will affect how he develops.
This is why it is important to give your child the best start in life you possibly can in terms of care and nutrition, because even the best laid plans can go awry if they are not given the right conditions for growth. With all the wonderful variety of human life, it is one of the most exciting privileges of parenthood to watch your baby become his very own person, familiar in so many ways, but also unique.
