A-J Review Sheet (Central Dogma of Biology) Part A: What does the acronym DNA stand for? ___Deoxyribonucleic Acid_____________________ It was discovered that the smallest section of a DNA molecule that can still be considered DNA is called a nucleotide. One DNA nucleotide consists of 1 Five Carbon _sugar + 1 phosphate group + 1 nitrogen base. Two scientists, Watson and that DNA consists of a double_ helix alternating Crick determined , in which the sides are composed of sugar (deoxiribose) & phosphate groups , and in which the steps (rungs) are composed of 2 nitrogen bases held together by a weak Hydrogen _ bonds. The sequence of the bases (or rungs of the ladder) is unique for each person and provides a blueprint / recipe for how to make the human body. 1. To serve as the genetic code for any organism, a DNA molecule must be capable of storing large amounts of varying information. How does the structure of a DNA molecule help it store large amounts of information? Spirals (double helix) and then coils around Histone proteins 2. Why is DNA often called the blueprint for life? Because it contains the instructions for how to build a body like blueprints have the instructions for how to make house Part B: DNA is the blue print of life. DNA is found within the nucleus billion of every cell in the human body. It is approximately 3 nucleotides long and contains thousands or millions of genes. These genes, can be read like the chapters in book – each telling their own unique story. In the 1990’s scientists embarked on an important project to sequence the entire human genome are 99.9 % identical to each other and . During this project they discovered that humans 50 % identical to bananas! Since the conclusion of this project scientists have begun to use the sequence to find the causes of diseases in humans. Some of the diseases they have linked to our DNA are: tay sachs, cancer, Alzheimer’s, . . , and . While we are still unable to cure all the worlds diseases, we hope that learning more about our DNA we will help us someday achieve this goal. Part C: To serve as the genetic code for any organism, a DNA molecule must also be capable of copying itself. When does a cell replicate its DNA? Cell replicates its DNA during the S phase of interphase to guarantee that each new cell created during division will have an exact copy. The process of DNA replication begins when the weak Hydrogen _ bonds break with the help of the helicase enzyme. This allows the DNA molecule to unzip down the middle of its length resulting in 2 open strands. Immediately the enzyme DNA polymerase attaches new nucleotides and C to each open strand of DNA, with A _always attaching to T always attaching to G. Finally the 2 newly formed DNA strands zip back up and recoil to form 2 identical DNA double- helixes . Each DNA helix is 50 new DNA. This follows the semi-conservative replication a mutation % parental DNA and 50% model. When an error occurs during can occur. However, the specific enzymes within the nucleus check for these ‘mistakes.’ Part D: What does the acronym RNA stand for? _Ribonucleic Acid RNA differs from DNA since it uses Ribose to make a single nucleus ___ sugar and the nitrogen base stranded molecule. All RNA is made in the of eukaryotic cells through the process of . All living things on Earth contain three types of RNA. ribosomes, while tRNA mRNA Uracil transcription rRNA is used to build relays information from the DNA to the ribosome, and . transfers amino acids to where they are needed. Part E: An essential step in the process of protein synthesis is transcription of the DNA code to mRNA. Transcription occurs in the nucleus of the cell where the DNA is located. The process of transcription begins when a section of DNA called a promoter allows a single strand of mRNA is controlled by an enzyme called complementary unzips and _to form along it. The process of unzipping the DNA RNA Polyermase . The RNA strand that is produced is a . copy of the original DNA. For example if the DNA template strand reads ATC GAT then the RNA will read UAGCUA until the ribosome reaches a stretch of DNA called a . This process continues terminator . A codon is a specific group of There are 64 while three code for 3 nitrogen bases on a mRNA molecule. different codons. Sixty-one of these codons attract a specific amino acid, stop . AUG is the start codon. Part F: An essential step in the process of protein synthesis is translation of the mRNA codon into a functioning protein. Translation occurs in the 20 cytoplasm of the cell and requires the presence of life’s . common amino acids. These amino acids are present in our cells thanks to the food we eat. Translation begins when a ribosome begins to move along a mRNA strand read its codons. At the start ___ to codon the first tRNA anticodon will attach. From here, as each codon is read it will attract a specific anticodon or tRNA molecule ,which will bring a specific amino acid with it. These amino acids will connect to each other, one at a time, by a peptide bond. The process continues until the ribosome reaches a stop codon. At this point the mRNA, tRNA and rRNA will be released from one another so they can be recycled within the cell. The chain of amino acids is called a ___polypeptide . This molecule will then combine with other polypeptides, fold forming Hydrogen bonds and create a functional protein . Part G: Critical Thinking Questions: 1. Why don’t all human beings look and act identical? (use the words DNA and protein in your answer) Our genome is slightly different. Therefore our DNA is transcribed into slightly different codons of mRNA which are translated into different sequences of amino acids. We do not have the same proteins. 2. Think about what DNA and protein is composed of (hint their monomers). Where does your body get the nucleotides and amino acids needed to make more DNA and protein? We get the nucleotides to build new DNA and RNA, and the amino acids to build new proteins from the food that we eat. 3. Let’s say I wanted to build a protein that was 500 amino acids long… a. How long would the DNA that codes for that protein be (in terms of bases)? 1500 b. How long would the mRNA that codes for that protein be (in terms of bases)? 1500 c. How many codons of mRNA would code for that protein? 500 d. How many tRNA molecules would need to be used to make that protein? 500 Part H: Comparing DNA to RNA – place at least 6 pieces of information in the Venn Diagram Double Helix Deoxiribose Sugar Thymine A, C, G phosphate sugar backbone Single Stranded Ribose Sugar Uracil Part I: Comparing replication, transcription and translation. Process Where it Occurs Replication Nucleus Transcription Translation Nucleus Cytoplasm What molecules are involved DNA, DNA helicase, DNA polyermase DNA, all types of RNA, RNA polymerase mRNA, tRNA, rRNA, amino acids, various enzymes and ATP (energy) Where it starts and stops All over (bubbles form and eventually connect) Promoter to terminator Start codon to Stop codon What it creates DNA All types of RNA Protein Part J: Comparing mRNA, tRNA, and rRNA Type of RNA Structure Function mRNA Single short strand (3 letters = codon) Carry the message of how to make the protein tRNA Folded t like structure carrying an amino acid (3 letters = anticodon) Transfer the ingredients for the protein (amino acids) rRNA Folded into a ribosome Make the protein Part K: Coding DNA template DNA complementary strand mRNA codon tRNA anticodon amino acids (remember to use codons) ATA CGC GGG TAT GCG CCC UAU GCG CCC AUA CGC GGG Tyr – Ala- Pro