Why is everyone's DNA so unique?
The part of dna which makes us unique
In science, the term recombination refers to the critical process in human genetics that helps scientists find a diverse genome with bits of DNA from both our ancient and recent ancestors. Understanding recombination is what helps learn about human inheritance and uniqueness.
Human DNA is 99.9% identical from person to person and the 0.1% difference actually represents millions of different locations within the genome where variation can occur.
We inherit two copies of each chromosome, one copy from our mom and one copy from our dad, meaning that our genome is already different because it contains chromosomes from both of our parents. This can also help explain why two siblings appear to have different genetic ancestry, since they may get different chromosomes from their parents.
But there is more: the actual sequence of DNA on each of the chromosomes is unique due in part to recombination and the process of making gametes, known as sperm or egg cells.
Recombination is a process where sections of DNA are traded between the chromosomes that make up a pair. After recombination, the chromosomes will look somewhat like a quilt because they are made up of DNA from both parents. The total amount of DNA on each chromosome should not change in a significant way, because a portion of our mom’s chromosome was traded for the same portion on our dad’s chromosome.
But how does this create a unique sequence? The human DNA sequence consists of nearly 3 billion DNA base pairs and the order of these base pairs is nearly identical from person to person, but sometimes there are random changes in the sequence and we call these changes variants. The combination of all of our variants make up the 0.1% difference in our DNA and helps give us a unique sequence. This means when chromosome pairs come together, the chromosomes we inherit from our mom are slightly different from the chromosomes we inherit from our dad thanks to the many DNA variants on each of the chromosomes.
When recombination happens, the chromosomes are essentially trading DNA variants amongst themselves. This process helps drive evolution by creating a slightly new version of the DNA: each chromosome we have is a unique quilt of DNA, representing segments of the genome that have been passed down from generation to generation. This shuffling has helped drive evolution through time, and ultimately has helped write our genome and our story.