DNA-RNA


 * DN ﻿ A and RNA **


 * Structure of DNA:﻿﻿﻿ **
 * ** DNA stands for Deoxyri ﻿ bonucleic Acid **
 * ** Made of Nucleic Acids **
 * ** store and transmit ge ﻿ netic information **

** There are three parts of a nucleotide: **
 * ** Nucleotides are the monomers or the things that make up nucleic acids. [[image:dna_bases.gif align="right"]]**
 * 1) ** Phosphate (acid) **
 * 2) ** Deoxyribose (sugar) **
 * 3) ** Nitrogenous Base ( Adenine, Cytosine , Guanine , and Thymine )**




 * Among the nucleotides, there are two types of nitrogenous bases: **
 * ** Purine: Double ( Adenine and Guanine )    **
 * ** Pyrimidines: Single ( Cytosine and Thymine ) **


 * Rules for Base Pairing: **
 * ** There are rules that apply to the DNA Structure **
 * ** These rules will always apply and never change (unless it is RNA) **
 * ** Cytosine (Pyrimidine) to Guanine (Purine) **
 * ** Thymine (Pyrimidine) to Adenine (Purine) **


 * RNA:[[image:dna_versus_rna_reversed.jpg width="363" height="413" align="right"]] **
 * ** RNA stands for Ribonucleic Acids **
 * ** RNA is similar to DNA except for these things: **
 * 1) ** Has only one strand instead of two strands **
 * 2) ** Uracil pairs up with **** Adenine (instead of **** Thymine ) **
 * 3) ** In the nucleotide, it has ribose as its sugar (instead of **** Deoxyribose ) **
 * 4) ** Has three types of RNA not one **
 * 5) ** Used for short-term storage instead of long-term **
 * ** As you can see in the picture to the right, there are definite differences between DNA and RNA **


 * Types of RNA: **
 * ** There are three main types of RNA **
 * ** All three are made in the nucleus **
 * ** Below are the three types and their functions **


 * Messenger RNA (mRNA): **
 * ** This type of RNA acts as a "messenger". It carries a copy of the directions from the DNA in the nucleus to the ribosome in the cytoplasm. **



** Ribosomal RNA (rRNA): **
 * ** This RNA is part of the ribosome which is made up of proteins and rRNA. **

** Transfer RNA (tRNA): **
 * ** This last RNA type transfers an amino acid to the ribosome. **

** DNA Replication: **
 * ** DNA replication takes place in the nucleus and is the process that makes DNA itself. **
 * ** There are three major steps in DNA Replication **
 * ** Before DNA Replication begins, it needs: **
 * ** DNA **
 * ** Free DNA Nucleotides **
 * ** Helicase and DNA Polymerase (enzymes) **

** Step #1: **
 * ** When the double helix (DNA) unwinds the 2 strands of the DNA and they separate from one another, DNA Replication begins. **
 * ** __//Helicase//__ will unzip or separate the DNA[[image:DNA_Replication_1.jpg width="660" height="140"]] **

** Step #2: ** >
 * ** Each strand works as a template upon which a new, missing half is built. **
 * ** DNA Polymerase will move up and down the DNA strands making new strands as they go along **
 * ** //__﻿﻿﻿DNA Polymerase__// builds new DNA **


 * Step #3: [[image:semiconservative.jpg width="224" height="224" align="right"]] **
 * ** Every double helix will contain one old and one new DNA strand **
 * ** This is called Semiconservative **
 * ** As you can see to the right, the picture has strands that are semiconservative **
 * ** The red strand is the old strand or parent strand **
 * ** The blue strand is the new strand or daughter strand **
 * ** The two strands are identical to one another **

** Summary: ** **
 * ** DNA replication assures that new cells will carry the same genetic information as each other and as the parent cell. It occurs in the nucleus of a cell and has three major enzymes involved in the process. These enzymes are helicase which unwinds the DNA strands, DNA polymerase which will make new DNA strands after the DNA has spilt and it will also proofread, and DNA ligase proofreads the DNA. As a result of this process, there will be an identical copy of the DNA. For additional information on DNA Replication or DNA structure, click on the additional links below.


 * Below is an animation and three additional sites about DNA replication that will help you understand the process better. **
 * ** Animation: **[|DNA Replication]


 * [|DNA Structure and Replication]
 * ** The bottom part is gone over in the next section **
 * [|DNA Structure and Replication]
 * ** You do NOT need to know about the last section titled Polymerase Chain Reaction (PCR) **
 * [|DNA Replication Animation]