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DNA Student Lecture Notes CHAPTER 12 To understand genetics, scientists had to understand the __________________of each gene. If gene structure can be identified, then understanding how genes are inherited can be understood. In 1928 Fredrick Griffith was trying to figure out how bacteria made people sick. He was looking at the bacteria in pneumonia. He isolated 2 strains of bacteria, where each strain looked different on a Petri dish. One strain _______________________, one strain didn’t. He killed off the harmful strain from heat, but left the bacterial ‘body’. 1. Killed-harmful strain injected into mice = no death 2. Injected LIVE harmless strain into mice= no death 3. Dead harmful and live harmless= ____________________ *Results: The living harmless somehow received harmful material from the dead strain. This is called _________________________________. Harmless was somehow transformed into harmful. AVERY 1944 Avery repeated the experiment to try to figure out which __________________ in a cell is causing pneumonia. His team ended up systematically killing all proteins in one trial, all fats and carbs, in another trial, even killing RNA. Yet, the dead strain STILL transformed the non lethal strain. Avery finally used an enzyme that destroyed the DNA of the bacteria. Only then was the dead strain was unable to transform. This proved that _______ stores and transmits genetic information form one __________________________ to the next. HERSHEY- CHASE 1952 pg 289 They worked with _______________________. Viruses were considered non living because they didn’t follow all the characteristics of life. One type of virus is called a bacteriophage. It infects bacterial cells. These viruses are very, very small and contain only RNA or DNA. A bacteriophage will attach to a specific cell (based on its shape) and inject its DNA or RNA into the cell. This viral DNA enters the ________________________ and attaches to existing DNA. This cell now makes ______________________, rather than a regular cell. Before the cell bursts, it can have ____________________________ of new viruses produced in the cell. Radioactive Markers. Martha Chase and Hershey wanted to know if the shape of the virus protein or the DNA was entering the cell. This would tell them if genes are in protein or in DNA. Proteins contain no phosphorus, but DNA does. DNA contains no sulfur. When they looked at infected cells, they all contain ___________________________. This proved that DNA contains genetic material, and proteins do not contain ___________________. DNA does 3 critical things 1. Transfers genetic information to each ___________________________. 2. DNA must be copied with each cell _____________________________. 3. DNA has to function to make new ________________________. DNA is made of: a sugar deoxyribose A phosphate group One of 4 nucleotides; Adenine, Guanine, Cytosine, Thymine (AGTC) CHARGAFF concluded that A’s are connected to ___and that G is connected to ______ A-T, G-C. ROSILAND FRANKLIN showed that DNA is twisted in shape, in helix, where the nitrogen bases are in the middle. She looked at it through X-rays. WATSON AND CRICK Using Franklin’s x- rays, they constructed the first model of the _________________ __________________. Their paper was one page long and they won the Nobel Prize. Hydrogen bonds are what kept A bonded to T and G to C. DNA Beads How is your strand similar to your partners? How is your strand different from your partners? Compare your sequence to others. How is it similar? How is it different? Chromosomes and DNA Replication DNA molecules are very long. E coli (bacteria) have over 4 million base pairs. This is about the same as you having 300 meters (3 football fields) of rope on your backpack. Eukaryotic cells have DNA even more tightly packed. Now your backpack has 30 miles of rope. One microscopic skin cell has enough DNA to stretch 1 _____________. To make this possible, to fit into the nucleus, the DNA is tightly coiled and proteins called ___________________ hold them together. During mitosis, the coils get tighter to form specific chromosomes. A nucleusome is DNA coiled to fit into the nucleus. Each DNA strand folds around histone proteins. Then the coils coil around into super coils, which form the nucleosome. DNA Replication Once the double helix was formed it was easy to see how it could be replicated. Part of the double Helix can dismantle, by the breaking of the hydrogen bonds holding the _________________. In the S phase of a cell cycle, the double helix unwinds, making two strands; Enzymes are a vital part of DNA replication. Polymerase, Ligase, Helicase, are a few of the enzymes. DNA helicase unzips the DNA by breaking the hydrogen bonds. Each strand is now the template for the other strand. ATGCATGCATGCATGC TACGTACGTACGTACG (Original DNA Sequence) A T G CATGCATGCATGC GTACGTACGTACG (Unzipping, breaking hydrogen bonds) C A T After the DNA unzips, new individual nucleotides begin to attach to the old DNA strand with the help of an enzyme called DNA polymerase. This enzyme also “proofreads” the old DNA template DNA. Vitamin B-12 is used to help this enzyme. Ligase reattaches the hydrogen bonds, resulting in two identical DNA strands. A T T A G C CATGCATGCATGC G GTACGTACGTACG TC A A T ATGCATGCATGCATGC TACGTACGTACGTACG ATGCATGCATGCATGC TACGTACGTACGTACG (Unzipping, adding nucleotides) (Original DNA Sequence) (Replicated counter sequence) (Replicated counter sequence) (Original DNA Sequence) Both strands are exactly the same. pg. 300 Sometimes the entire DNA strand doesn’t need to be replicated, just a small portion, such as for the production of a new ___________________________. This is when RNA will attach to the original DNA strand. RNA is used for the purpose of __________________ ___________________. RNA is single stranded. RNA doesn’t have thymine. Instead of a “T” it has an Uricil, “U”. There are several types of RNA; Messenger RNA (________), ribosomal RNA (_________), transfer RNA (_______). Most of your DNA genes code for proteins. Proteins are made of __________ ____________. These amino acids are assembled on ribosomal RNA. Steps for protein synthesis 1. Part of the DNA unwinds 2. The enzyme RNA polymerase helps mRNA attach to unwound part of DNA. The mRNA makes a copy of the DNA protein code. 3. The mRNA detaches from the DNA strand and the DNA double helix reforms, with the help of DNA ligase. 4. Notice that the RNA strand is backwards. DNA mRNA tRNA ACCTGTCAA UGGACAGUU ACCUGUCAA (same as DNA) CATGCATGC GU ACGU ACG (mRNA) ATG TGC TACGTACGTACGACG (Original DNA Sequence) GUACGUACGU tRNA with amino acid attached CATGCATGC GUACGUACG (mRNA) 5. This tRNA also has an amino acid (the primary structure of a protein) attached to it. Primary protein structure How does the mRNA know where to attach and when to stop? Within the DNA, there are starting regions (promoter) and stopping regions. The start regions have a code TAC. The stop codes represent TGA, TAA, and TAG. This is how scientists know that some type protein was being coded in the DNA, when they would see TAC followed later by stop code. CCA AAC TGC GGA TACGGA GTC GGG TTA CTT CAC GAG AAA TTC TGA TGC GGA GTC RNA editing 302 Within the DNA “TAC” and a stop code, there are extra parts that do not makeup the protein. The RNA must edit, or cut these parts so that only the protein code is in the mRNA sequence. The parts that are cut out are called introns. The parts that are left (the real code for a protein) are called __________. TAC TTC BLA BLA BLA CAA ACA UGA mRNA AAG GUU UGU tRNA UUC CAA ACA The “BLA” must be cut out before it can code The BLA, the _______ code, and the________ are not in the mRNA sequence because they do not code for a protein. Gene to protein, genetic code pg 302. A protein is made of poly “many” peptide chain of amino acids. The simplest proteins have thousands of amino acid chains. The tRNA has an amino acid attached to it. There are ______amino acids, and therefore 20 types of tRNA. The mRNA sequence which has the code to make the amino acid chain is read in 3’s, and called a ________. UAU codes for the amino acid tyrosine, UGG codes for tryptophan. UCG-CAC-GGU Serine – Histodine - Glycine Amino acid chain There are 64 codons, but 6 code for leucine. Translation Factory- Making, of the primary protein 1. 2. 3. 4. 5. 6. 7. 8. DNA unwinds mRNA assembles on the DNA attaches to DNA strands mRNA detaches, removes introns. mRNA moves to a ribosome, called ribosomal RNA transfer RNA begins to attach one at a time to the mRNA strand tRNA leaves the amino acids when it detaches from the mRNA. The amino acids chain (polypeptide chain) continues to grow until the last tRNA attaches. the polypeptide chain goes to the endoplasmic reticulum to make its protein shape. It travels to the Golgi to put its outer coating on. 9. the final protein is now functioning. 10. many proteins are enzymes that help the cell or organism function. ALL JACKED UP- When DNA goes BAD- mutations Mutations are changes in the DNA sequence, which affects genetic information. There can be gene mutations or chromosomal mutations. Many mutations involve just one change of a nucleotide. These are called __________ mutations. Sickle Cell Anemia is a point mutation. The substitution of nucleotide causes red blood cells to be crescent shaped instead of round. There is no cure for this disease. Sickled RBC Substitution: when one nucleotide is __________ with another. Deletion: when one nucleotide is __________ from the sequence. Insertion: when one nucleotide is ___________ to the sequence. Normal THE Substitution: THE FAT CAT FAT CAT ATE THE ATE THE RAT BAT Normal RBC DNA TAC GCA TGG AAT .mRNA AUG CGU ACC UUA Amino Acid Met---Arg---Tro---Leu mutated DNA mRNA Amino Acid TAC GTA TGG AAT AUG CAU ACC UUA Met---His---Tro---Leu A ____________________ mutation occurs when a nucleotide is added or deleted. Frameshift mutations render the entire protein useless. Normal Insertion: Deletion THE FAT CAT ATE THE RAT THO EFA TCA TAT ETH ERA T TEF ATC ATA TET HER AT Sometimes and entire ____________ can be added or deleted. These effects can be less harmful that a frameshift mutation. Normal insertion codon Deletion codon THE THE THE FAT CAT ATE THE RAT BIG FAT CAT ATE THE RAT CAT ATE THE RAT ________________________ happens when one codon is moved into a different location. Normal Translocation Translocation THE THE ATE FAT CAT ATE THE CAT ATE THE FAT THE FAT CAT THE RAT RAT RAT Chromosomal Mutations pg308 This involves changes in the number of chromosomes or the removal or addition of parts. Duplication involves doubling a chromosome or some part of a chromosome. People with Downs’ Syndrome have three chromosomes at the 18th or 21st homologous set. Inversion involves pair of the chromosome break and reforming in the wrong spot. ABCD EFGHIJK EFABC GHIJK Translocation This involves non-homologous pairs transferring chromosomal material. (example chromosome 5 and 12 crossing over). This is not the same as Cross Over in Meiosis.