What is DNA?
DNA is like a big book of information that tells the cell what to do. It's like the boss of the cell, controlling everything that happens inside. One important job it has is to tell the cell how to make proteins, which are like little workers that do different tasks. It does this by using a special code that can be turned into specific molecules that the cell needs. Now, let's find out more about how the CEO of the cell works!
The structure of the DNA
Structure of DNA
DNA, short for deoxyribonucleic acid, might sound like a weird name, but it actually makes sense. In cells called eukaryotic cells (which are most cells that aren't bacteria), DNA takes the form of a double helix, which means it looks like a twisted ladder. This double helix is made up of two strands, and each strand is made of smaller building blocks called nucleotides. These nucleotides are connected to each other and to nucleotides on the opposite strand. The chain of each strand is made up of two important parts - phosphoric acid, which is an inorganic component, and deoxyribose, which is a type of simple sugar. And finally, deoxyribose connects to one of four nitrogenous bases.
Nitrogenous bases are small molecules that come together to create a genetic code. In DNA, there are four different types: Cytosine (C), Guanine (G), Adenine (A), and Thymine (T). We don't need to worry about their detailed structure, but it's important to know that each base can only pair with one other specific base because of how they are shaped. For example, cytosine always connects with guanine, and adenine always pairs with thymine. The type of base determines the type of nucleotide it is a part of. For instance, a nucleotide with adenine is called an adenine nucleotide. To keep things simple, each nucleotide is represented by a letter, which is the first capital letter of its name. The bonds between the bases hold the double helix shape of DNA together. The order of nucleotides on a strand is known as a sequence.
The genetic code
Nucleotides always pair up the same way, like A with T and G with C. If we know the sequence on one side, we can figure out the sequence on the other side. Nucleotides are like a code with four bases, but what does it mean? Well, proteins are made up of 20 different amino acids, and they have a complex structure that can be broken down into a sequence of amino acids.This is where the genetic code comes in. Three nucleotides make up a codon, which represents one amino acid. Cells can decode this information to create the amino acid chain needed to make a specific protein. The genetic code chart helps us decode the code easily (each three-letter sequence represents a different amino acid, and stop codons tell the cell to stop decoding). You don't have to memorize everything; just use the chart when you need it.
The Genetic Code
Characteristic of Genetic Code
- The genetic code is the set of rules by which a linear sequence of nucleotides specifies the linear sequence of a polypeptide.
- That is, they specify how the nucleotide sequence of an mRNA is translated into the amino acid sequence of a polypeptide.
- Thus, the relationship between the nucleotide sequence of the mRNA and the amino acid sequence of the polypeptide is the genetic code.
- The nucleotide sequence is read as triplets called codons.
Comparison of DNA and RNA
RNA is a type of molecule that is similar to DNA but has some key differences. It is made of ribose sugar instead of deoxyribose sugar, and it contains uracil (U) instead of thymine (T).
During the process of transcription, DNA strands separate slightly, and an RNA molecule is created that is compatible with one DNA strand and identical to the other.
Once the RNA molecule is properly formed, it can leave the nucleus and travel to other parts of the cell. In the next section, we will learn more about how proteins are made in the cell and how DNA replication occurs.
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