If you’ve ever been a soon-to-be parent, you’ve likely wondered what your child will look like. Will they have your partner’s blue eyes? Or how about your thick, curly hair? Will they inherit your in-law’s height, or be short like your family?
What your child will look like all comes down to genes. While we know more than we used to, there is still a lot scientists don’t understand about how genes work. For this reason, it is impossible to predict with one hundred percent accuracy what your newborn is going to look like.
Genes Determine What Your Child Will Look Like
“If we examined all a fetus’s DNA, we still wouldn’t be able to truly anticipate things,” says Barry Starr, Ph.D., geneticist in residence at The Tech Museum, in San Jose, California .
That being said, you can look at you and your partner’s genes to make some educated guesses as to what your child will look like when they’re born. Genes, however, are complicated. Even though you receive half of your genes from your father and half from your mother, that doesn’t mean that you’re going to be a perfect blend of the two. This is because some genes are dominant, and others are recessive.
Dominant Vs. Recessive Genes
Dominant or recessive refers to the relationship between two versions of a gene. When a baby is conceived, they receive two versions of each gene from each parent. These are called alleles. An example of these genes could be the eye color gene, the hair color gene, the height gene- the list goes on.
If the alleles, or version, of the two genes are different, one will be expressed over the other. This is the dominant gene. The other gene is the recessive .
Examples of dominant traits include:
- Dark hair
- Curly hair
- Almond-shaped eyes
- A widow’s peak (having a V-shaped hairline)
Examples of recessive traits include:
- Blonde or red hair
- Straight hair
- Round eyes
- A straight hairline 
To explain how this dominant and recessive genes work, consider the following example:
The mother has dark, curly hair, and no freckles. The dad has blonde, curly hair, and has freckles. While you can’t say with one hundred percent certainty what their child will look like, the most likely scenario is this:
The child will inherit curly hair because both parents have that dominant gene. They will likely have dark hair from the mother, and have freckles from the father.
Now, if the mother also has the gene for blonde hair in her DNA, it is possible for the child to end up with blonde hair. It is also possible that they won’t be born with freckles, because again, genetics is not a perfect science and we cannot predict with perfect accuracy what someone will look like before they’re born.
What About Eye Color?
Eye color is even more complicated because it is a polygenetic trait. This means that more than one gene controls what eye color you will have.
At least two genes will influence the color of your baby’s eyes. Each of these genes also has two alleles: a brown and blue version, or a green and blue version. How they are all related is as follows:
- Brown is dominant over green
- Blue and green are dominant over blue
- Brown is dominant over blue green
- Green is dominant over blue
The following are examples of how parents’ eye colors will affect that of their children:
- If either parent carries the gene for brown eyes, more than likely the child will have brown eyes.
- If one parent carries two blue alleles and the other carries a blue and a green, the child will likely have green eyes.
- If one parent has two blue alleles and the other has two green alleles, the child will probably have green eyes.
- If both parents have two blue alleles, the child will most likely have blue eyes .
In addition, the color of your baby’s eyes when they’re born may not be the color they end up with.
“The color-producing cells in the iris need exposure to light to activate,” explains Dr. Starr .
Similarly, as your child grows, other things can impact the expression of their genes. For example, a child with blonde, straight hair may go through puberty and their hair may darken, or start to curl.
What Else Impacts What Your Child Will Look Like?
To make matters more confusing, yours and your partner’s genes are not the only genes that will influence your baby’s looks. Your parents, or even your great-grandparents, can also have an effect on what your child will look like.
This is because certain physical traits can skip a generation. For example, red hair and blue eyes can both skip a generation because they’re recessive. Other reasons traits can skip a generation (or two, or three) are:
- By chance due to a phenomenon called genetic drift.
- An environmental change that makes the trait a disadvantage (aka natural selection).
- The trait has what is called “incomplete dominance” (an example of this is a cleft chin) .
To understand this, let’s use the example of red hair. Imagine you have two non-red hair genes. We’ll call this RR. Your partner, on the other hand, has bright red hair, and therefore has two red hair genes (since red is recessive). They, then, have the rr gene.
Just so you’re keeping track:
RR = not red
rr = red
If you have a child, they will end up with the Rr hair gene. They will have non-red hair because the ‘r’ gene is recessive.
Imagine, then, that your child grows up and meets a partner with the RR gene. The Rr spouse has a fifty/fifty shot at passing down an R or and r. That means that their children could end up with the red hair gene, or they could not. Either way, the child is more likely to have non-red hair.
If this ‘r’ gene continues to be passed down, however, there is a chance that it could be expressed in later generations, under the correct circumstances .
It’s All a Guessing Game
Despite how much we analyze things, genetics is not an exact science. We may have a better understanding of how genes work than we once did, but our knowledge is still quite limited. For this reason, there is no way to accurately predict what your child is going to look like.
If you are expecting a child, however, there is one thing you can be certain of: your baby is going to be beautiful regardless of whether or not they get your eyes or your partner’s nose.