DNA Structure and Replication

True/False Indicate whether the sentence or statement is true or false.

____ 1. Even though they contain weakened or killed infectious organisms, vaccines can still cause an immune response when injected into an organism. ____ 2. Even though Avery’s experiments clearly indicated that genetic material is composed of DNA, most scientists at that time continued to suspect that proteins were the genetic material. ____ 3. Bacteriophage are a type of bacteria that infects viruses. ____ 4. Hershey and Chase were the first two scientists to prove that genetic material is composed of proteins. ____ 5. The five-carbon sugar in DNA nucleotides is called ribose. ____ 6. A nucleotide consists of a sugar, a phosphate group, and a nitrogen base. ____ 7. Franklin’s X-ray diffraction images suggested that the DNA molecule resembled a tightly coiled spring, a shape called a helix. ____ 8. Chargaff observed that the amount of adenine in an organism always equaled the amount of thymine. ____ 9. Wilkins and Franklin were the first to suggest that the DNA molecule resembled a tightly coiled helix. ____ 10. The strands of a DNA molecule are held together by hydrogen bonding between adenine with guanine molecules and cytosine with thymine molecules. ____ 11. After replication, the nucleotide sequences in both DNA molecules are identical to each other and to the original DNA molecule. ____ 12. The two areas on either end of the DNA where the double helix separates are called replication forks. ____ 13. DNA polymerases have the ability to check for errors in nucleotide pairings.

Completion Complete each sentence or statement.

14. A(n) ______is a harmless version of a disease-causing microbe that can stimulate a person’s immune system to ward off infection by the infectious form of the microbe. 15. Griffith’s experiment showed that live bacteria without capsules acquired the ability to make capsules from dead bacteria with capsules in a process Griffith called ______. 16. The ability of a microorganism to cause disease is referred to as its ______. 17. Avery’s prevention of transformation using DNA-destroying enzymes provided evidence that ______molecules function as the hereditary material. 18. Viruses that infect bacteria are called ______. 19. A DNA subunit composed of a phosphate group, a five-carbon sugar, and a nitrogen-containing base is called a(n) ______. 20. The name of the five-carbon sugar that makes up a part of the backbone of molecules of DNA is ______. 21. Watson and Crick determined that DNA molecules have the shape of a(n) ______. 22. Chargaff’s observations established the ______rules, which describe the specific pairing between bases on DNA strands. 23. Watson and Crick used the X-ray ______photographs of Wilkins and Franklin to build their model of DNA. 24. Due to the strict pairing of nitrogen bases in DNA molecules, the two strands are said to be ______to each other. 25. The process by which DNA copies itself is called ______. 26. The enzyme that is responsible for replicating molecules of DNA by attaching complementary bases in the correct sequence is called ______. 27. Enzymes called ______are responsible for unwinding the DNA double helix by breaking the hydrogen bonds that hold the complementary strands together. 28. Errors in nucleotide sequences are called ______. 29. Errors in nucleotide sequencing are corrected by enzymes called ______. 30. The circular DNA molecules in prokaryotes usually contain ______replication forks during replication, while linear eukaryotic DNA contains many more. DNA Structure and Replication Answer Section

TRUE/FALSE

1. T 2. T 3. F 4. F 5. F 6. T 7. T 8. T 9. T 10. F 11. T 12. T 13. T

COMPLETION

14. vaccine 15. transformation 16. virulence 17. DNA 18. bacteriophages 19. nucleotide 20. deoxyribose 21. double helix 22. base pairing 23. diffraction 24. complementary 25. replication 26. DNA polymerase 27. helicases 28. mutations 29. DNA polymerases 30. two