How Does a Baby Inherit Its Looks?


Expectant parents often spend hours imagining what their little ones will look like. Will they have mommy’s eyes, or daddy’s? Whose hair color will they inherit? Will the maternal or paternal traits win out? Or will there be a combination of both sides of the family?

Since there are often misconceptions about how a baby’s looks are inherited (including the myth that brown eyed parents can’t birth a blue-eyed baby, and vice versa), we are exploring how physical appearance is determined by our DNA.

DNA & Physical Appearance

Hair Color

Individuals inherit many gene pairs that are involved in determining hair color. So, both parents could carry recessive genes that pass along to their children, resulting in the child having a different hair color than their hair colors that were determined by dominant genes.

Genes involved in determining hair color are also involved in regulating melanocytes, our color-producing cells. So hair color can ultimately depend on the number of melanocytes they possess, what pigment they make, and how much of each shade the melanocytes produce. There are two types of melanocytes — eumelanin, which makes black to brown, and pheomelanin, which makes yellow to red. With more melanocytes that produce more eumelanin, the darker the hair; with fewer that produce mostly eumelanin, it’ll likely be light brown or blonde. With more pheomelanin production, the more likely she’ll have red hair.

Eye Color

Many babies are born with blue-gray eyes that eventually change color. This is because the cells in our irises that produce color need to be exposed to light in order to activate. This means that eye colors are usually not stabilized until at least six months.

There are at least two genes involved in eye color, and they can come in two alleles: one with brown and blue types, and one with green and blue types. A child’s eye color depends on the allele combination inherited from the mother and father.


While a number of factors can initially affect a baby’s size, such as the mother’s diet and health, there are also genes at play. There are over 100 genes that affect height, and unless poor nutrition, lack of exercise, or medical conditions such as type 1 diabetes get in the way, a child will typically grow to the size determined by their genes.

DNA Testing Can Confirm Relationships

You can never rely on looks alone to confirm or deny biological relationships. The only way to completely ascertain relationships is with DNA testing.

Test Smartly Labs of Lee’s Summit provides court-admissible, discreet, and confidential paternity and maternity testing as well as other types of relationship DNA testing. If you want DNA testing, call (816) 875-9301 today!

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