DNA Replication Worksheets

DNA Replication You may refer to the textbook or internet. Portions not completed in class is considered homework. You’re required to use your own paper (if needed) for Concept Checks and the recommended Chapter Review (examinable). Please bring this on quiz/ test days for teacher’s inspection and recording of Learning Skills. Past year questions (if any) may encompass more than one chapter or subtopics yet to be covered. Concept Checks (For suggested answers, see Appendix A of textbook). Answer the questions from either the eleventh (11e) or twelfth (12e) of the book edition which you’re using: 11e 1. Given a polynucleotide sequence such as GAATTC, explain what further information you would need in order to identify which is the 5′ end. (See Figure 16.5.) You can’t tell which end is the 5’ end. YOu need to know which end has a phosphate group on the 5’ carbon or which has a -OH group on the 3’ carbon. 11e/ 12e 2. VIsUAL sKILLs Griffith was trying to develop a vaccine for S. pneumonia when he was surprised to discover the phenomenon of bacterial transformation. Look at the sec- ond and third panels of Figure 16.2. Based on these results, what result was he expecting in the fourth panel? explain. He expected that the mouse injected with the mixture of heat-killed S cells and living R cells would survive, since neither type of cell alone would kill the mouse. ConCept CHeCK 16.2 11e/ 12e 4. VIsUAL sKILLs if the DNA Pol I in a given cell were nonfunctional, how would that affect the synthesis of a leading strand? in the overview box in Figure 16.17, point out where DNA Pol I would normally function on the top leading strand. Synthesis of the leading strand is initiated by an RNA primer which must be removed and replaced with DNA, a task that could not be performed if the cells DNA pol I were nonfunctional. 11e/ 12e ConCept CHeCK 16.3 1. Describe the structure of a nucleosome, the basic unit of DNA packing in eukaryotic cells. A nucleosome is made of 8 histone proteins, two each of four different types, around which RNA is wound. Linker DNA runs from one nucleosome to the next. 1 Q1. The following two figures represent experiments by early researchers that led to the discovery of DNA as genetic material. Experiment ‘A’ 2 Experiment ‘B’ (a) Identify the researchers of experiments ‘A’ and ‘B’ above. (2 marks) A: Hershey Chase B: Griffith and Avery 3 (b) The earlier research of DNA used bacteria instead of eukaryotes. Explain why choosing bacteria over other organisms allowed early success. You may refer to experiments ‘A’ and ‘B’ above to help you. (5 marks) Eukaryotic cells have nucleus and cell organelles with a large amount of DNA present, where were prokaryotic cells have no nucleus, no organelles and a very small amount of DNA. Bacteria were chosen so that there weren’t too many independent variables in the experiment, just DNA. Q2. Chargaff’s rule was developed out of a different research plan. Chargaff looked for differences in DNA among different species. Here is the data collected from his research (see table below). What differences (in different species’ DNA) can you determine from this data? (2 marks) 4 With the aid of the figure below, describe the process of DNA replication. Include reference to specific proteins and their functions. (5 marks) DNA replication is the process of producing two identical copies of DNA, in which each template for the synthesis of a new complementary daughter strand. The central enzyme involved is DNA polymerase, which catalyzes the joining of deoxyribonucleoside 5'-triphosphates to form the growing DNA chain. The points where the DNA first are opened are called replication origins.DNA replication begins at a single origin of replication, and the two replication forks assembled there proceed in opposite directions until they meet up roughly halfway around the chromosome. 5 3. Using the table below, list any four (4) enzymes involved in DNA replication. For each enzyme, briefly describe its function and what would happen if it were not present. (Assume the absence of any one enzyme does not affect the activity of others) (6 marks) Enzyme Function Absence of Enzyme Helicase Unwinds the DNA double helix No DNA replication as it can’t start Gyrase Relieves the buildup of torque during unwinding No torque is relieved therefore double helix can snap. Primase Lays down the RNA primers DNA is not duplicated as RNA is not placed DNA polymerase I Replaces RNA primers with DNA The DNA strand would not be a duplicate or much functional as the double helix would contain both RNA and DNA. 6