Do you ever wonder exactly how you got the features that you have? Why you have a different colored hair than your parents? Well for starters, you must know that all traits are inherited. Lets say this is the scenario; You have blonde hair, but both your parents have brown. Think to your grandparents. Did any of them have blonde hair? In this scenario the answer would be yes, because as you will see later on,, the recessive gene, ( Blonde hair ) Cant show through when it is paired with a dominant gene, ( Brown hair ).
But im getting ahead of myself. Lets start from the beginning.
If you go way way way back, you will come upon the very first thing that was, well, you. The very first cell that you formed from, called a zygote, performed a process called mitosis to form your body. Mitosis is when one cell copies its genetic information, (Chromosomes) and splits in half giving you a whole new cell.
This keeps happening over and over again and continues to happen now as your body grows. But back on track. When we go back to the zygote we find all forty-six of your chromosomes, twenty-three from mom and twenty-three from dad. For every chromosome that you get from your mom, you get one from your dad that pairs up with it.
( Not the ones you wear)
When you look deeper, youll find that the chromosomes are made up of genes, while each of our genes are made up of segments of DNA. ( Deoxyribonucleic Acid ) Which look like a twisted ladder.
Link to Picture
Each gene is a trait that will be represented. Some traits, such as height, are determined by not just one gene, but multiple. Since Chromosomes come in pairs, so do genes. Therefore, for every chromosome you get from your dad and for every one you get from your mom, you get multiple genes that match up to each other. (one from each parent) These become your genes which determines your traits.
Dominant or Recessive?
Now back to the original question. Why did the person in the scenario have blonde hair, but both your parents have brown? In the beginning we looked back to the grandparents, and there was one grandparent with blonde hair on either side,the other being brown haired. The chart to the left shows the mother and father’s genes for blonde or brown hair. (NOTE: there is more than one gene determining hair color.) Both are hybrids, meaning that they have one dominant and one recessive gene. The Brown, which is dominant, Is the big B while the blonde is the little one. They have one brown haired gene from their brown haired parent and a blonde gene from their blonde haired one. After completing the punnett square shown above, you can see that they would have had a 25% chance of having a purebred dominant, a trait represented with two dominant genes, a 50% chance of having a hybrid, a trait represented with one dominant and one recessive genes, and a 25% chance of having a purebred recessive, a trait that is represented with two recessive genes. Therefore, they have a 75% chance of having a brown haired child, because in the hybrid the dominant gene overpowers the recessive one, and a 25% chance of having a blonde haired child.
In conclusion, you cant have a blonde haired kid if you have no blonde hair in your family whatsoever, because for the recessive gene to come through it needs to be paired with another recessive one. I was just using this as an example though, because human genetics is way more complicated when you bring in things like red and black hair, curly or straight. If you are really interested in learning about genetics, I hoped this helped start you of with the basics.