Quick Answer
There is a chance that your baby will have red hair if the father has red hair, but it is not guaranteed. The gene for red hair is recessive, so both parents must carry the gene for there to be a possibility of the child having red hair. If the father has red hair and the mother carries the red hair gene, there is around a 50% chance of the child having red hair. However, the specific probability depends on the gene variants present in each parent.
Genetics of Red Hair
Red hair is caused by variants of the MC1R gene. This gene codes for a protein involved in pigment production. There are several different variants of the MC1R gene associated with red hair:
- Arg151Cys
- Asp294His
- Arg160Trp
- Asp84Glu
To have red hair, an individual must have two copies of an MC1R red hair variant, one inherited from each parent. If someone has only one copy of a red hair variant, they will still be a carrier for red hair but their hair will not be red.
The variants most strongly associated with red hair are Arg151Cys and Asp294His. Having two copies of one of these variants almost always results in red hair. The other variants have weaker effects and may result in red hair only when two copies are present.
Probability of a Child Having Red Hair
As the gene for red hair is recessive, the probability of a couple having a child with red hair depends on the MC1R gene variants present in each parent:
If one parent has red hair and the other has brown/blonde hair:
- The red-haired parent has two copies of a red hair variant.
- The non-red parent is assumed to carry one copy of a red hair variant.
- Each child has a 50% chance of inheriting the red hair variant from both parents and having red hair.
- Each child has a 50% chance of inheriting only one red hair variant and having brown/blonde hair.
If both parents have red hair:
- Both parents have two copies of a red hair variant.
- Each child will inherit one red hair variant from each parent.
- The probability of each child having red hair is 100% in this case.
If one parent has red hair and the other has black/dark brown hair:
- The red-haired parent has two red hair variants.
- The non-red parent has no red hair variants.
- None of the children will inherit two red hair variants, so the probability of red hair is 0%.
To summarize, the father having red hair does not guarantee the child will have red hair. But it does mean there is a chance, provided the mother carries a recessive red hair gene variant as well. The exact probability depends on the genotypes of both parents.
Other Genes That Influence Red Hair
Although variants of the MC1R gene have the largest effect on red hair, other genes can also influence hair color:
- TYRP1 – Involved in melanin production. Certain variants are associated with red hair.
- ASIP – Encodes the agouti signaling protein. Variants can suppress red hair caused by MC1R.
- OCA2 – Encodes the P protein which controls melanin synthesis. Red hair variants may interact with MC1R.
- SLC45A2 – Encodes a melanocyte transporter protein. Contributes to red hair in an unknown way.
The variants present in these additional genes likely influence the shade of red hair. But MC1R plays the primary role in determining red versus non-red hair.
Other Factors That Affect Red Hair Expression
Modifier Genes
Other unknown genes likely modify the effects of MC1R variants. The expression of red hair can vary quite a bit between individuals with the same MC1R genotypes. Other genetic factors influence whether red hair is brightly colored or more strawberry blonde.
Environment
Sun exposure and vitamin D production may also affect natural hair color, along with other environmental variables. Lifestyle and health conditions during fetal development could potentially impact hair pigmentation later in life as well.
Conclusion
The father carrying red hair gene variants means there is a chance of passing on red hair, but the specific probability depends on the mother’s genetics as well. If the mother does not carry any red hair variants, it is not possible for a child to have red hair, even if the father has bright red hair. The MC1R gene has the biggest impact on red hair inheritance, but other genetic and environmental factors can modify the final hair color. To predict the odds of a child having red hair, DNA tests of both parents can help determine the presence or absence of specific MC1R red hair variants.