Does Every Cell in the Human Body Contain the Same DNA?
With few exceptions, all cells in a person’s body have the same DNA and genes. As cells divide and grow different genes are expressed, resulting in different cell types. Those cells then produce a variety of proteins specific to the cells they form resulting in most of our chemistry. In general, the same is true for all cell-based life on earth.
All Cells Start as One Cell With the Same DNA
- All cells start as one cell, the fertilized egg created from your mother’s egg and a father’s sperm.
- Each of which contains 1/2 of the DNA that makes a person a unique person (unless they have an identical twin).
- That first fertilized egg cell “divides” from conception to adulthood into about 37 trillion cells rotating cells, with each cell containing the same exact DNA (with exceptions).
- As the cells divide they express different genes, which give many cells unique functions.
There are about 20,000 human genes in a given person’s DNA, but most are dormant or “not expressed” in any given cell. When sets of genes are expressed they create one of 200 different types of cells. Each cell type makes a set of 100,000 or so different proteins made up of 20 amino acids. These proteins, along with the cells, perform most functions in a human body.
FACT: Human genes are like specific “lines of code” in a cell’s DNA that makes each of us who we are. Some of the code is the same for everyone, but some is unique to you unless you have an identical twin, in which case you share the same DNA.
What are the Exceptions? What Cells Don’t Contain the Same DNA?
Almost all cells have the same DNA, but there are a few exceptions.
- Mature red blood cells which contain no DNA
- The sperm and the egg that have half the amount of DNA
- B cells in which some of the DNA has been rearranged to make antibodies.
A video discussing what is DNA and how does it work?
What is DNA and How Does it Work? Simplified
DNA is a the code for life, DNA creates little snippets of code called RNA, RNA is read by ribosomes, ribosomes make amino acids, amino acids form proteins, and proteins create life.
In other terms, DNA is a bunch of atoms stuck together that form a code for making a life. In humans, DNA contains human gene codes. That gene code in the DNA tells amino acids how to form themselves into proteins using three letter sequences. These sequences dictate which amino acids should be added next to create a specific type of protein. Those proteins perform most of the different functions of the human body. This is why some people call DNA “the blueprint” and amino acid “the building blocks” of life.
The Process of DNA becoming proteins: RNA and Ribosomes
DNA’s genetic code is contained within the nucleus of a cell. For that code to get out of the cell and start making proteins it has to be copied and transferred outside the cell in small chunks. These copies are called RNA. The RNA is small enough to escape the nucleus, travel out through the cells cytoplasm, and inserted into ribosomes contained within the ribosomes.
The ribosome reads the RNA code and gathers corresponding amino acids, which it forms into corresponding proteins.
FACT: The DNA of all life is made up from 4 different bases (nucleotides): adenine (A), thymine (T), guanine (G) and cytosine (C). These 4 letters are printed in specific sequences on long strands of DNA, copied by RNA, and read by ribosomes in sequences of 3. This is all that is needed to create you and all life on earth.
Proteins and Genes
Each gene is essentially just a recipe for making a specific protein. Proteins account for about 1/2 of cells dry weight and do all of the heavy work in your body: digestion, circulation, immunity, communication between cells, motion-all are made possible by one or more of the estimated 100,000 different proteins that your body makes.
An Analogy to Understand Protein is Made From DNA.
Imagine that DNA is like all the code on your computer (it’s not useful unless we tell the computer what parts of code to use), RNA is like a specific lines of code that make up a program, ribosomes read the lines of code and execute a given program by creating amino acids (which are like the pixels that display on your screen, the way those amino acids line up form images which we can equate to proteins. You could think of the cells as being like the hardware and the screen itself.
How Does DNA Know What Type of Cells to Make?
Even though your cells are genetically identical every time a cell’s splits each cell has the chance of having a different destiny depending upon factors like where it is in the body (asymmetric cell division), cells changing from one type to another is called cellular differentiation. So the DNA and the cells themselves don’t know what type of cell to make, rather certain genes in the DNA are “expressed” (turned on) when a cell splits and then the above process from DNA to protein fires off a unique part of the code.
Are Cells Different Than Protein?
Proteins are the chains of amino acids that perform a large part of your bodies functions, cells are the different types of cells that have split from the original fertilized egg. Cells produce the proteins, but proteins don’t produce cells. Thus, you are made up, mostly, of cells and proteins.
FACT: Cells, proteins, and DNA are all made up of atoms.