When we think about what gets passed down from parent to child, most people imagine a mix, mum’s eyes, dad’s nose, a little bit of both when it comes to height or personality. But science says some traits come exclusively from dad. Not shared. Not blended. Straight from father to child.
Here are 7 things children inherit only from their father
Biological sex
It is probably the most well-known fact, a child’s sex is determined entirely by the father’s contribution. Women carry two X chromosomes (XX), while men carry one X and one Y (XY). It’s the sperm that determines whether the baby gets another X (and becomes female) or a Y (and becomes male). But what many don’t realise is that this isn’t entirely random; some men are statistically more likely to father boys or girls depending on the balance of X- and Y-bearing sperm they produce.
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Y chromosome traits (for sons)
The Y chromosome is passed only from father to son, and it carries very specific information, mainly instructions for male development. This includes the formation of testes, sperm production, and the development of male secondary sexual characteristics like facial hair and voice depth. Since the Y chromosome has fewer genes than the X, it doesn’t code for many general features, but what it does carry is key to male identity and fertility. If a father has a mutation on his Y chromosome, there’s a strong chance his son will inherit it too.
Male pattern baldness
There is a popular myth that baldness is inherited from your maternal grandfather. But while there’s a gene on the X chromosome that influences hair loss, recent studies suggest that the father’s genetics also play a significant role, especially in early-onset male pattern baldness. If a father starts losing hair before 40, there’s a strong chance his son might experience the same. The genetic story here is more complex than once thought, but the dad’s side of the family can be a telling predictor, especially for sons.
Certain genetic disorders
Some rare but serious genetic disorders are linked directly to the Y chromosome, which means they’re passed only from father to son. These include conditions like Y chromosome infertility, where a man may have low sperm count or poor sperm quality due to deletions on the Y chromosome. While these disorders are rare, they’re critical because they can affect fertility and, in some cases, have knock-on effects for hormonal health and development.
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Height potential
Height is influenced by both parents, but researchers have found that paternal genes play a slightly stronger role in determining a child’s maximum growth potential. If a father is very tall or very short, it’s more likely that his children will lean towards his height, especially sons. There are multiple genes involved in height, many of which regulate bone growth and hormone sensitivity. These can be more dominant when passed down from the father’s side. That said, nutrition and lifestyle also play a big part, so genes only tell part of the story.
Risk of Achondroplasia
Achondroplasia is the most common cause of dwarfism and is usually caused by a spontaneous mutation in the FGFR3 gene. What’s fascinating is that this mutation is almost always passed down through the father’s sperm, and the risk increases with paternal age. While most cases are not inherited (they occur as new mutations), when they are, they come exclusively from the father.
Heart disease risk
Although lifestyle is a major factor, genetic predisposition to heart disease can come from the father’s side, particularly for males. Some heart-related genes on the Y chromosome affect inflammation and cholesterol regulation, potentially increasing a son’s risk. Studies have found that men with fathers who suffered early heart attacks or cardiovascular issues are at greater risk themselves, even if they follow a healthy lifestyle.
