Chapter 10 The Structure & Function of DNA California State Standards covered by this chapter: Name Date Period Cell Biology 1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept: Students know how prokaryotic cells, eukaryotic cells (including those from plants and animals), and viruses differ in complexity and general structure. d. Students know the central dogma of molecular biology outlines the flow of information from transcription of ribonucleic acid (RNA) in the nucleus to translation of proteins on ribosomes in the cytoplasm. Genetics 4. Genes are a set of instructions encoded in the DNA sequence of each organism that specify the sequence of amino acids in proteins characteristic of that organism. As a basis for understanding this concept: Students know the general pathway by which ribosomes synthesize proteins, using trnas to translate genetic information in mrna. Students know how to apply the genetic coding rules to predict the sequence of amino acids from a sequence of codons in RNA. Students know how mutations in the DNA sequence of a gene may or may not affect the expression of the gene or the sequence of amino acids in an encoded protein. d. Students know specialization of cells in multicellular organisms is usually due to different patterns of gene expression rather than to differences of the genes themselves. e. Students know proteins can differ from one another in the number and sequence of amino acids. f.* Students know why proteins having different amino acid sequences typically have different shapes and chemical properties. 5. The genetic composition of cells can be altered by incorporation of exogenous DNA into the cells. As a basis for understanding this concept: Students know the general structures and functions of DNA, RNA, and protein. Students know how to apply base-pairing rules to explain precise copying of DNA during semiconservative replication and transcription of information from DNA into mrna. Read the appropriate section in the textbook and lecture notes before answering the following questions. You must put all answers and definitions in your own words for full credit. DNA Structure and Replication 1. The is the site where nucleic acids are synthesized and it therefore directs the activities of the cell. 2. DNA stands for. 3. DNA is composed of repeating subunits, or monomers, called. 4. The basic structure of a nucleotide includes 3 main parts. List them and include a labeled diagram. Structural Part Labeled Diagram
5. The nitrogenous bases of DNA include: Nitrogenous Base Class of organic molecule (purine or pyrimidine) d. 6. Describe the difference between the structure of a purine and the structure of a pyrimidine. 7. What does the backbone of DNA consist of? Describe how it is assembled and what holds it together. 8. What is the overall shape of DNA? 9. The double helix structure was first described in 1953 by and. 10. Were it not for the X-ray crystallographic photograph of DNA, taken by, these gentlemen would not have deduced the structure of DNA when they did. 11. The rungs of the twisted ladder are of uniform length because in each case one base is a doubleringed and the other is a single-ringed. 12. The 2 strands of DNA are held together by between the bases. 13. What is the base-pairing pattern seen with the nucleotides of DNA? 14. Why are the 2 strands of DNA said to be complementary strands? 15. Along one strand of a double helix is the nucleotide sequence GGCATCGCAATTCGGCAT. What is the complementary sequence for the other DNA strand?
16. The process of the duplication of a DNA molecule is called. 17. During which specific phase of the cell cycle does DNA replication take place? DNA Replication NOTE: You will need to use the lecture notes to assist in some of your answers. 18. Why is it important that DNA replication occurs simultaneously at many points along the molecule? 19. What important roles do enzymes play during the replication process? Enzyme Role (function) DNA helicase Primase DNA polymerase DNA ligase 20. Prokaryotic cells lack a nucleus; eukaryotic cells have a nucleus. Suggest an adaptive advantage for confining DNA in a nucleus. (Hint: Think!!) The Flow of Genetic Information from DNA to RNA to PROTEIN 21. List 3 ways in which a molecule of RNA differs structurally from a molecule of DNA. (Review previous readings and the lecture notes.)
22. Three types of RNA are made from DNA in the nucleus. Complete the following table after reading pp.181-184 in your book and the lecture notes. RNA Molecule Abbreviation Description/Function Messenger RNA Transfer RNA Ribosomal RNA 23. DNA stores and transmits the information needed to make proteins but it does not actually use that information to synthesize proteins. That is the primary function of, which stands for. 24. codon: 25. protein synthesis: 26. Protein synthesis involves 2 main stages. Complete the following table. Process Location in Cell where process takes place Function Transcription Translation 27. genetic code: 28. How many different amino acids are there? 29. is transcribed using DNA as a template. The genetic code inherent in the DNA is thus reflected in the sequence of bases in mrna. A specific group of sequential bases of mrna is called a. Each codon codes for, or recognizes, a specific using as an intermediary. Each codon attracts a group of bases on trna, and each trna has a specific amino acid attached to it.
30. There exist possible codons. Most encode amino acids, but a few encode start signals that engage a to start reading an mrna molecule or stop signals that cause the ribosomes to stop reading mrna. 31. The universal start codon is. 32. A particular protein is 200 amino acids long. In the gene for this protein, how many nucleotides are necessary to code for this protein? Explain. 33. With the limitation of so few different amino acids, what makes one protein different from another? Use the dictionary of the genetic code (RNA codons) to answer the following questions. 34. An mrna molecule contains the nucleotide sequence CCAUUUACG. Translate this sequence into the corresponding amino acid sequence. 35. An mrna molecule contains the nucleotide sequence AUGAAAGCCGAUUAA. Translate this sequence into the corresponding amino acid sequence. 36. A DNA molecule contains the nucleotide sequence TACTTAGCCGAT. Give the corresponding mrna sequence and translate the sequence into the corresponding amino acid sequence. Transcription 37. Transcription takes place in the of the cell. 38. First, attaches to the region of a specific gene in DNA. 39. unwinds the by breaking the bonds between the nucleotide strands.
40. then adds complementary nucleotides in the direction to create the primary transcript of mrna. 41. This continues until the RNA polymerase reaches the sequence on the DNA. 42. The is released and the primary transcript of mrna is also released. RNA Processing/RNA Splicing Before the mrna can leave the nucleus and enter the cytoplasm, it must have some modifications made to it. 43. First, a is added to the 5 end of the mrna strand and a is added to the 3 end of the mrna strand. 44. Then the are removed from the primary transcript of mrna and the are spliced together to form the final mrna. 45. Introns are the regions of DNA and exons are the regions of DNA 46. This final transcript of mrna exits the nucleus and enters the. Translation 47. First, the ribosomal subunit attaches to the mrna at the start codon,. 48. Next, the initiator carrying the complementary attaches to the start codon on the mrna. 49. This trna carries the amino acid. 50. Then the ribosomal subunit attaches to the mrna/ribosomal complex so that the initiator trna is located in the site. This forms a functional complex that will translate the rest of the mrna sequence. 51. An incoming carrying the complementary to the next codon enters the site. 52. The amino acid on the trna at the site is transferred to the amino acid on the trna at the site and a bond is formed between the amino acids, creating a polypeptide chain. 53. The trna in the site moves into the site and is released. The trna in the
site moves into the site and the site is now empty. This step is known as translocation. 54. Another incoming carrying the complementary to the next codon enters the site. 55. The polypeptide chain on the trna at the site is transferred to the amino acid on the trna at the site and a bond is formed between the amino acids, creating a longer polypeptide chain. 56. The trna in the site moves into the site and is released. The trna in the site moves into the site and the site is now empty. 57. This process of elongation continues until a is reached. There are 3 stop codons,,, and. 58. When the ribosome reaches the, the polypeptide chain is released and the two ribosomal subunits detach. 59. Each protein molecule is made up of one or more polymers called, each of which consists of a specific sequence of linked together by. 60. What is the difference between a promoter and a terminator? What are they used for? Mutations 61. DNA mutation: 62. mutagen: 63. mutagenesis: 64. carcinogen: 65. List 3 factors that can damage DNA:
66. Complete the following table that describes the different types of mutations within a gene. Type of Mutation Description Results of Mutation Base insertion Base deletion Base substitution 67. Are all mutations bad? Explain. Viruses: Genes in Packages 68. Virus: 69. Describe the structure of a typical virus. 70. What are the similarities between viruses and cells? 71. What are the differences between viruses and cells? 72. bacteriophage: 73. lytic cycle:
74. Describe what is happening at each step in the Lytic cycle diagram below. d. e. f. 75. Describe what is happening at each step in the Lysogenic cycle diagram below. (g) d. e. (f) f. g. 76. What are three ways in which a plant virus can infect a plant?
77. What effects do plant viruses have on plants? 78. Describe how an enveloped RNA virus is able to replicate. 79. retrovirus: 80. Describe how it is possible for a retrovirus to replicate without having DNA. 81. HIV: 82. AIDS: 83. Describe the steps of replication for a retrovirus such as HIV in the diagram below. 1. 2. 3. 4. 6. 5. www.txtwriter.com/backgrounders/aids/aids3.html
84. At what point is an individual with HIV said to have developed AIDS? 85. Some people suggest that the drug AZT (aidothymidine) can help patients with AIDS. This drug blocks the enzyme reverse transcriptase. Explain how AZT might help patients. 86. Why might scientists think that viruses evolved after cells?