Section: The Structure of DNA Read each question, and answer based upon what you learn in the section. 1. What did Griffith discover, what was his conclusion, as a result of his experiments? Transformation; that genetic material can be transferred between bacteria. The foundation of heredity. 2. How did Avery discover that the material responsible for transformation in bacteria was DNA? He performed Griffith’s experiments, but with more precision. 3. Viruses that infect bacteria are called [bacteriophages / rough]. A virus is made of DNA and [proteins / cell walls]. Radioactive sulfur was used to label the [DNA / protein] in the viruses. Radioactive phosphorus was used to label the [DNA / protein] in the viruses. Hershey and Chase discovered that after the 32P-labeled phages infected the bacteria, most of the radioactive phosphorus was found in the layer containing [bacteria / phage]. 4. Hershey & Chase are given credit for discovering what? Discovering that DNA is the genetic material. 5. Describe each research group’s contribution to the discovery of DNA’s structure. a. Chargaff: Base-pairing rules. A-T, C-G b. Franklin & Wilkins: 1st x-ray diffraction image of DNA, give insight into structure. c. Watson & Crick: Nobel prize-winning combo that 1st correctly predicted the structure of DNA Match the letter of the phrase with the appropriate term 6. __h___ double helix 7. __d___ nucleotides 8. __a___ deoxyribose 9. __b___ hydrogen bond 10. __c___ nitrogenous bases 11. __f___ adenine 12. __e___ cytosine a. a five-carbon sugar b. type of weak bond between base pairs that holds the double helix together c. four kinds and they form specific pairs d. subunits that make up DNA e. one of two pyrimidines used as a nitrogenous base in nucleotides f. one of two purines used as a nitrogenous base in nucleotides g. discovered that the amount of adenine always equaled the amount of cytosine and that guanine always equaled cytosine h. two strands of nucleotides twisted around each other 13. __g___ Chargaff Describe each feature of DNA below 14. Complementary: one strand matches the other, not mirror images but fits together like hands. 15. Anti-parallel: the backbones are parallel but run in opposite directions, like a twolane highway. 16. Backbone: outside regions of the molecule. composed of repeating molecules of phosphate groups and 5-carbon sugars 17. Nucleotides: subunits of nucleic acids. Made of a phosphate group, 5-carbon sugar, and a nitrogen base. Sketch a nucleotide. --------------------------------------------------------------------------- Purines: category of nucleotide with 2-ringed nitrogenous bases A & G Pyrimidines: category of nucleotide with 1-ring nitrogenous bases: T, C, & U Hydrogen Bonds: the weak type of bond that holds the 2 strands of DNA together between the nitrogen bases. 22. Base-pairing rules: based off of Chargaff’s rules. A double bonds with T, C triple bonds with G 23. 32% A %A = %T (32%), 100% - (%A + %T) = (%C + %G). 100% - 64% = 36%. 18% C & 18% G. 18. 19. 20. 21. Section: Gene Expression, Transcription & translation Match the letter of the phrase with appropriate term 1. __b___ribonucleic acid (RNA) a. the entire process by which genes are used to build proteins/traits. b. a molecule made of linked nucleotides 2. __f___uracil c. the process of reading instructions on an RNA molecule to put together the 3. __e___transcription amino acids that make up a protein 4. __c___translation d. a 3-nucleotide sequence of mRNA e. the process of transferring a gene’s instructions for making a protein to an RNA 5. __a___gene expression molecule 6. __d___codon f. a nitrogenous base used in RNA instead of the base thymine found in DNA Complete each statement by identifying the correct term or phrase in the brackets. 7. Transcription begins when [RNA / RNA polymerase] binds to the gene’s promoter. The promoter region contains the sequence [AUG / TAC]. RNA polymerase adds complementary [DNA / RNA] nucleotides as it “reads” the gene. In eukaryotes, transcription takes place in the [nucleus / cytoplasm]. Read each question, and write your answer in the space provided. 8. What are three differences between RNA & DNA? Has uracil instead of thymine, single-stranded instead of double, ribose instead of deoxyribose. 9. What determines where on the DNA molecule transcription begins and where it ends? The start sequence TAC and the stop sequences ATT, ATC, ACT Describe the role of each RNA molecule. 10. mRNA: is the RNA transcript of the gene in DNA. Carries the gene recipe to the cytoplasm 11. tRNA: is the link between genetic material (RNA) and amino acids. Carries amino acid corresponding to the codon. 12. rRNA: structural component (along with protein) of ribosomes. Complete each statement by identifying the correct term or phrase in the brackets. 13. Translation takes place in the [nucleus / cytoplasm]. It uses the molecules called [rRNA / tRNA] to bring [proteins / amino acids] to the [E.R. / ribosome] by matching their [anti-codon /codon] to the complementary [anti-codon / codon] in [DNA / mRNA]. 14. Study the following six steps in the synthesis of proteins. Determine the order in which the steps take place. Write the number of each step in order. _______a. 2. The codon following the start codon then receives the tRNA molecule with the complementary anticodon. The tRNA carries the amino acid specified by the codon. _______b. 6. Steps 2–5 are repeated until a stop codon is reached. The newly made protein is released into the cell. _______c. 4. The first tRNA detaches, leaves behind its amino acid, and moves away from the ribosome. _______d. 3. Enzymes help form a peptide bond between the amino acids of adjacent tRNA molecules. _______e. 5. The tRNA (with its growing protein chain) and mRNA move one codon down, and the next codon is ready to receive the next tRNA and its amino acid. _______f. 1. An mRNA, the ribosome, and a tRNA carrying the amino acid methionine bind together. The tRNA bonds to the “start” codon AUG.