What is the difference between a chromosome and a gene? What is a gene? What do genes do?

What is the relationship between DNA and genes? Every cell has a function. If you're a muscle cell, you've got to contract. If you're a brain cell, you've got to think. If you're a pancreatic cell, you've got to produce insulin. Every cell has certain sets of functions. That function of the cell is dictated by the code of DNA, and the unit that codes for each protein that is giving every cell its characteristics is the gene. The gene may comprise 50,000 of these base units. I said we have 3 billion of these base units. An individual gene may be 10,000, 50,000, or about 100,000 of these units. So it's a small segment of the DNA that codes for the function of the proteins that that cell is making. What is an allele? An allele is the genetic distinction of the two copies you may get of a single protein gene. If I have a gene that makes insulin, I actually have two. I got one from mom and I got one from dad. Each of those genes are considered an allele. Remember, everybody's unique. It turns out that the sequence of dad's allele may be a little different than the sequence of mom's allele. In fact, you as an individual have two alleles. You have a copy of a gene from dad and a copy of a gene from mom. They're about 99.9% identical, but there may be some slight genetic differences in the two copies, and we refer to those as allelic differences. What are genetic traits? The color of your hair, the color of your eyes, everything that you look like is derived from your genes. That's why you kind of look a little bit like mom. You might look a little bit like dad because you're getting genes from both of those, so they give you your traits. The important thing for people to recognize is it's easy to see how genes can vary to give you different traits because if you sit in a room of a lot of people, everybody looks different. Let's move that one step further. You look different on the inside too. Your cells internally, the genes that they express are just as unique inside you as the traits that you have outside of you.