The Structure and Role of DNA
So, what is DNA? DNA is short for deoxyribonucleic acid. In other words, it's the control center for what you look like. DNA controls everything from what color your hair is to how tall you are. DNA controls all of your physical features and can be found in all of your body cells.
DNA is in the shape of a double helix. We like to think of it as a twisted ladder. The outside "poles" of the ladder are made up of sugar and phosphates. This isn't any ordinary sugar, though. This is deoxyribose sugar. This is where the deoxyribose comes from in deoxyribonucleic acid. The "rungs" of the ladder on the inside are made up of nucleobases, otherwise known as bases. There are four kinds of bases; guanine, cytosine, adenine, and thymine. These bases will always be connected to the sugar on the "poles" of the ladder (the phosphates basically just act as bridges for the sugars to be connected). Adenine and thymine will always connect, and guanine and cytosine will always connect. For example, if there's an adenine on one side of the "ladder", then there must be a thymine on the other side that connects to it. Same thing with guanine and cytosine.
There are also nucleotides in the DNA structure. A nucleotide is made up of one phosphate, one deoxyribose sugar, and one of the four bases. And there aren't just a few nucleotides here and there. There are million upon billions of nucleotides in a single DNA strand; a complex series of codes that determine only a single trait.
When the genetic code gets mixed up, and the bases don't connect right, we have mutations. A mutation is when a base is either added, removed, or substituted for another base. These mutations could effect many codons (a group of three bases that determines a certain amino acid to give) or just a few. When this accident happens, a mutation occurs. All mutations aren't necessarily bad. In fact, most mutations make no difference. A mutation will either be positive, neutral, or negative. An example of a positive mutation is being immune to a certain sickness; this mutation would be passed down to future generations, therefore making your family impossible to contract that certain sickness. An example of a negative mutation is a cat with no tail; an important part of a cat's balance is it's tail - if it lost it's tail, it would have poor balance. An example of a neutral mutation is two different eye colors; sure it looks cool, but it's neither beneficial or harmful. One little thing could change a lot!
As you can see, DNA is very confusing, but it gets simpler once you get to know it. To make things even easier for you, please click on the images below.
DNA is in the shape of a double helix. We like to think of it as a twisted ladder. The outside "poles" of the ladder are made up of sugar and phosphates. This isn't any ordinary sugar, though. This is deoxyribose sugar. This is where the deoxyribose comes from in deoxyribonucleic acid. The "rungs" of the ladder on the inside are made up of nucleobases, otherwise known as bases. There are four kinds of bases; guanine, cytosine, adenine, and thymine. These bases will always be connected to the sugar on the "poles" of the ladder (the phosphates basically just act as bridges for the sugars to be connected). Adenine and thymine will always connect, and guanine and cytosine will always connect. For example, if there's an adenine on one side of the "ladder", then there must be a thymine on the other side that connects to it. Same thing with guanine and cytosine.
There are also nucleotides in the DNA structure. A nucleotide is made up of one phosphate, one deoxyribose sugar, and one of the four bases. And there aren't just a few nucleotides here and there. There are million upon billions of nucleotides in a single DNA strand; a complex series of codes that determine only a single trait.
When the genetic code gets mixed up, and the bases don't connect right, we have mutations. A mutation is when a base is either added, removed, or substituted for another base. These mutations could effect many codons (a group of three bases that determines a certain amino acid to give) or just a few. When this accident happens, a mutation occurs. All mutations aren't necessarily bad. In fact, most mutations make no difference. A mutation will either be positive, neutral, or negative. An example of a positive mutation is being immune to a certain sickness; this mutation would be passed down to future generations, therefore making your family impossible to contract that certain sickness. An example of a negative mutation is a cat with no tail; an important part of a cat's balance is it's tail - if it lost it's tail, it would have poor balance. An example of a neutral mutation is two different eye colors; sure it looks cool, but it's neither beneficial or harmful. One little thing could change a lot!
As you can see, DNA is very confusing, but it gets simpler once you get to know it. To make things even easier for you, please click on the images below.
Genes and Proteins
DNA makes up another important part that controls who you are and what you look like: Genes. A gene is a segment of DNA that carries heredity instructions and are passed from parent to offspring. The gene carries all of the genetic coding in the DNA that makes up who you are. Usually certain traits are controlled by multiple genes. For example, your eye color is made up of multiple genes. That's why there can be many shades of a certain eye color. A white leopard's eye color will also determine it's skin color. There are dominant traits and recessive traits. You get a combination of two from your parents. Going back to eye color, brown eyes are dominant over blue eyes. This means that if you have even only one dominant trait, it will overpower the recessive trait and your trait will be the dominant one. You need all of your traits to be recessive in order to have that recessive trait appear. For example, if your mom has blue eyes (two recessive traits because you need two recessive in order to have blue eyes), but your dad has brown eyes (which could be either two dominants or a dominant and a recessive, but we'll just say a dominant and a recessive) then chances are you will have brown eyes. But you still have a chance of having blue eyes. In order to find this out. we use a Punnett Square. A Punnett Square is tool used for finding the likelihood of certain traits. View the image below to see the Punnett Square for a heterozygous brown eyes (which is one dominant trait and one recessive trait as mentioned before) and a homozygous blue eyes (two recessive traits).
The father has one brown-eyed, dominant trait, and one blue-eyed recessive trait. The mother has two blue-eyed recessive trait. When put together, you can see the combination is Bb, Bb, bb, and bb. Since the dominant (B) overpowers the recessive (b), then the squares on the left will be the children with brown eyes. The children on the right squares, however, will have blue eyes because they have two recessive traits. The chances of having a brown-eyed baby between this couple is 50% and the chances of having a blue-eyed baby is also 50%.
As you can see, the percentage of this couple having a brown-eyed baby and a blue-eyed baby are both the same. If the dad had homozygous brown eyes (two dominant traits), then there would be a 100% chance of having a brown-eyed baby, though. This is only one example of a trait. You can create Punnett Squares for every trait there is. Sometimes, the Punnett Square has even more than 4 boxes, but 9 boxes, 16, even 25. Genes might be even more confusing than DNA, but again, once you get familiar with it, it becomes very simple.
Proteins are another issue involving genes and DNA. Proteins, along with DNA, makes up a chromosome, which is an important part of cell division when they reproduce. Proteins do most of the work for the cell and are also the basic building block of a cell (they support the structure). Proteins are made up of Amino Acids, which are created by codons, a group of three bases. As you can see, without proteins, cells would cease to exist, and so would we.
Names to Know
There are several key people to know in the world of genetics and how it was discovered. Here are some of them.
James Watson & Francis Crick: James Watson and Francis Crick built the first accurate model of DNA. They discovered that DNA was actually in the shape of a Double Helix. They finished the model in April of 1953. James Watson was an American molecular biologist, geneticist and zoologist. Francis Crick was an English molecular sociologist, biophysicist, and neuroscientist. They used information from Rosalind Franklin to build their DNA model.
James Watson & Francis Crick: James Watson and Francis Crick built the first accurate model of DNA. They discovered that DNA was actually in the shape of a Double Helix. They finished the model in April of 1953. James Watson was an American molecular biologist, geneticist and zoologist. Francis Crick was an English molecular sociologist, biophysicist, and neuroscientist. They used information from Rosalind Franklin to build their DNA model.
Rosalind Franklin: Rosalind Franklin viewed the very first pictures of DNA using x-ray diffraction. Using these pictures, she and her partner Raymond Gosling, were the first to believe that DNA was in the shape of a helix. They thought, however, that it was a Triple Helix, not the a Double Helix. She was an English chemist and X-ray crystallographer. Watson and Crick stole her ideas to make their DNA model.
Erwin Chargaff: Erwin Chargaff unknowingly discovered that adenine always pairs with thymine and guanine always pairs with cytosine. He was an Austrian biochemist that helped contribute to the model of DNA with what he discovered.