Which physical traits are inherited from the father?

Physical traits inherited from the father include biological sex, characteristics linked to the Y-chromosome, height, and contributions like eye colour and dimples.

Here, we explore the science of genetic inheritance in more detail, and which characteristics are passed from father to child.

What are inherited genetic traits?

Inherited genetic traits are traits (genes) that are passed down from parent to child.

Our genes contain the information needed for a variety of processes that occur within the body, including instructions for growth and development, and instructions for making and maintaining our physical traits such as eye, hair, and skin colour.

The inheritance of genetic traits begins at conception when the sperm (male sex cell) fertilises the ovum/egg (female sex cell). Sex cells contain half the amount of genetic information of a somatic cell, which has 46 chromosomes (arranged in 23 pairs). Sex cells only contain 23 chromosomes.

When the sperm cell fertilises the egg, the DNA of the sperm and egg is combined, resulting in a fertilised egg (zygote). This zygote contains 50% DNA from the biological mother and 50% from the biological father, and divides to form new cells, passing on the same DNA to each cell.

This means that all somatic cells in the body contain the same genetic information.

Thanks to this process, observable traits, such as hair colour, blood type, or even the ability to roll the tongue can be seen in any biological children, proving that many traits are inherited or ‘passed down’, from parent to child.

What is the difference between inherited and acquired traits?

Not all our observable physical traits are inherited from our parents. Some traits are acquired, or gained, throughout our lives.

An inherited genetic trait is a physical characteristic/trait, that is passed down from one generation to the next via our genes.

Half of your DNA comes from your biological mother and the other half from your biological father. Your DNA also contains genes that encode important information for development and function, as well as for observable physical characteristics/traits (hair and eye colour, biological sex, and blood type).

Acquired traits are traits that are influenced by our environment, rather than being passed down from one generation to the next via genetics. These can include physical, mental, and emotional traits.

One example of this might be someone who enjoys exercising a lot. They may exhibit physical traits such as having a lean figure or being very muscular.

However, these traits have not been inherited i.e. their genes have not had a direct influence on their physique. Instead, their environment – in this case, the time they have spent exercising – has had a direct impact on their physical attributes.

An acquired trait might also be mental or emotional. Think about the last time you learnt something new – the more time you spend researching, observing and interacting with your environment, the more you experience, learn and develop.

Which genetic traits are inherited from the father?

Below are some of the genetic traits that are inherited directly from your biological father.

Biological sex

Fathers are directly responsible for the biological sex of their offspring.

Both males and females have 22 pairs of autosomal chromosomes, named 1 – 22. The 23^rd pair of chromosomes are the chromosomes that determine biological sex: males are XY and females are XX.

To understand how fathers are responsible for sex determination, we first need to understand the differences between somatic (body) cells and sex cells (gametes), and how sex cells are created.

The somatic cells in our body are also known as diploid cells. Diploid cells contain two copies of each chromosome.

In humans, gametes are only found in the reproductive organs. Female gametes are produced in the ovaries, and male gametes are produced in the testes.

Gametes are haploid cells. Haploid cells are created from diploid cells via a process called meiosis. Meiosis precisely halves the genetic material from a diploid cell to create haploid cells that have one copy of each chromosome.

Because female diploid cells contain two copies of the X chromosome, their sex cells (gametes) each contain one copy of the X chromosome.

However, male diploid cells contain one X chromosome and one Y chromosome. This means their sex cells will either contain one copy of the X chromosome, or one copy of the Y chromosome.

During conception, if the sperm cell that fertilises the ovum has an X chromosome, then the resulting zygote will be XX, and will develop into a female baby.

However, if the sperm cell that fertilises the ovum has a Y chromosome, then the resulting zygote will be XY, and the baby will be male.

This is why only fathers are responsible for the sex determination of their offspring – females can only pass on the X chromosome, whereas fathers can pass on an X or a Y chromosome.

Find out your baby’s sex from as early as 6 weeks’ into pregnancy, with our At-home Baby Gender Test.

Y-linked inheritance

Since all males inherit their Y chromosome exclusively from their biological fathers, some genetic disorders or other traits can be passed down from father to son.

There are very few inherited disorders or traits that are inherited between generations. This is partly due to the type and number of genes that are found on the Y chromosome.

Many genes on the Y chromosome are involved in sex determination and development. Genes that lie in the azoospermia factor regions (AZF) contain important genetic information for sperm cell production.

Since the Y chromosome is small, and many genes on this chromosome are responsible for sex determination and adequate sperm production, changes to or deletions of these genes can result in infertility.

For example, a deletion of one or several genes in the AZF regions means that very few sperm cells are made, if any at all.

This makes the chance of natural conception very difficult, if not impossible. Depending on the impact of the genetic changes on the Y chromosome, some men may be able to fertilise an egg, either naturally or through a process called IVF.

However, if they pass on the faulty genes of their Y chromosome to their sons, they too will also have the same infertility issues as their father. This is an example of Y-linked inheritance causing Y chromosome infertility.

Eye colour

It was thought that eye colour was inherited in a Mendelian pattern, however we now know that is not the case.

In fact, there are about 16 different genes that are responsible for your eye colour!

The genes that make the biggest impact on eye colour are HERC2 and OCA2, both of which are located on chromosome 15. These genes affect the quantity and quality of melanin in your eye, which impacts eye colour.

Both your mother and father pass on the genes necessary to produce your eye colour.

Puberty

Puberty is the process by which both males and females undergo physical maturation. Puberty typically begins at some point between the ages of 8 and 14, however it can begin even earlier or later than this.

Puberty is a slow process that takes several years to complete and encompasses many different physiological and emotional changes.

Females experience breast and pubic hair growth, menarche (first menstrual period) and the development of their reproductive organs such as the uterus and vagina.

Like females, pubescent males also grow pubic hair. Males will also experience an increase in both testicular and penis size.

The onset and development of puberty is polygenic, meaning that many genes are involved. These genes are passed on from both the mother and father.

Since the process is influenced heavily by genetics, scientists suggest that the onset of puberty is 50-75% inheritable (Manotas et al., 2022). This means that the timing of puberty is largely influenced by the genes you inherit from your mother and father.

At least one gene involved in pubertal timing in both male and female children – MKRN3 – is paternally linked i.e. passed down by your father.

MKRN3 is an imprinted gene, which means that one copy of the gene is silenced while the other is expressed. For MKRN3, only the allele from the father is expressed.

Some mutations (genetic changes) to the MKRN3 gene can cause something called central precocious puberty (CPP), the early onset of puberty. Children with CPP undergo puberty much earlier than their peers and reach sexual maturation at a younger age. It has several causes, but the importance of mutations in the MKRN3 gene as a cause of CPP have emerged within the last decade.

Therefore, when male or female children inherit an MKRN3 mutation from their father, they will develop CPP.

Height

Just like hair colour, eye colour, and even puberty, your height is controlled by multiple genes inherited from both your mother and father.

Scientists believe that genetics are responsible for around 80% of height variation. That means that if your parents are naturally very tall, it is likely that you will also be tall, because you have inherited genes that are associated with having a tall stature.

Some conditions may also contribute to a smaller than expected height. One example of this is coeliac disease, where damage to the intestine impacts the amount of nutrients the body can absorb. In children, this malabsorption can lead to a small stature.

Height is also influenced by your environment. The most important environmental factor that influences height in children is diet. Lack of dietary protein, as well as a lack of other important nutrients, can lead to slower growth and smaller height.

Dimples

Dimples are said to be an irregular dominant trait. This is because they aren’t inherited in a predictable pattern like other traits, such as hair colour or blood type.

Scientists do believe that certain genes are involved in the formation of dimples, but which genes they are remain unknown.

Some scientists think that dimples are mostly controlled by one gene but that others may contribute towards the development of dimples. Since dimples are believed to be highly inheritable in most cases, this provides strong evidence for the involvement of genes, as all our genes are passed down from our parents.

However, at present, there is no way to determine with certainty how dimples are inherited, or which genes are involved.

Fat storage

There are several genes which appear to be involved in the distribution of fat in the body.

Various studies have suggested genetic inheritance plays a significant role in fat storage, with some studies estimating that heritability of fat storage could be as high as 61%.

One study performed in England titled ‘Children of the 90s’, which sampled 6,000 people, found that some variants in the Melanocortin 4 Receptor (MC4R) gene were more likely to increase the risk of weight gain by causing an increase in appetite.

MC4R makes a protein that tells the brain how much fat you have stored in your body. If this gene is defective, then the brain thinks you have less fat than you actually do, which causes you to feel very hungry. This can lead to overeating. It can also be harder for people who have variants in this gene (MC4R deficient) to lose weight.

Changes to the MC4R gene can be inherited and can be found in family members within the same generation, as well as across several generations.

Mental health issues

There is evidence to suggest that mental health problems such as schizophrenia, anxiety, depression and bipolar disorder can run in families i.e. be passed down from parent to child.

Mental health issues are complex, and although there is some evidence that suggests our genetics do have a role in the development of some mental health disorders, there are many other factors at play, including environmental factors.

For example, if one of your parents has schizophrenia, then you are slightly more at risk of developing schizophrenia than the general population. If both of your parents have schizophrenia, then this risk significantly increases (Rethink Mental Illness, 2024).

However, there is a very good chance that you won’t develop schizophrenia, even if one or both parents have the condition. Other factors, such as drug or alcohol misuse, loneliness or stress can also play a big part in the development of certain mental health disorders.

Scientists have identified a significant number of genes which may play a role in in the development of mental health conditions, such as depression, anxiety, bipolar or schizophrenia, but having any one of these genetic variants does not mean that you are guaranteed to develop a mental health illness. In fact, the risk remains relatively low.

So, if your father suffers from a mental health condition, it may increase your risk of developing the same condition, but it remains relatively unlikely that you will, based on genetics alone.

Where can I get a baby gender test?

Of all the genetic traits that are inherited from the biological father, a baby’s sex is by far the most exciting for expectant parents.

And now, thanks to innovation from DNA testing laboratories like AlphaBiolabs, it’s easier than ever to find out your baby’s sex from as early as 6 weeks into pregnancy.

Our At-home Baby Gender Test allows you to find out your baby’s sex, with no need to make a clinical appointment, and only a small blood sample required.

Order your test kit online, and we’ll ship it out to you immediately. Your test kit will contain everything you need to collect your blood sample and return it to our laboratory for testing, including our innovative TinyTAP device and full instructions on how to use the device to collect your sample.

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Order your Baby Gender Test online now, call 01 402 9466 or email info@alphabiolabs.ie for more information.

*From receipt of your samples at our laboratory, before 10am.

**Additional fees apply.