After meiosis, gametes have the amount of nuclear DNA as somatic cells. a. one-third b. twice c. half d. the same

Transcription

1 Concept 9.1 DNA Structure Reflects Its Role as the Genetic Material After meiosis, gametes have the amount of nuclear DNA as somatic cells. a. one-third b. twice c. half d. the same

2 Concept 9.1 DNA Structure Reflects Its Role as the Genetic Material Without looking at your notes: 1. Name the two purine nucleotides of DNA. 2. Name the two pyrimidine nucleotides of DNA. 3. Which nucleotides pair up with one another?

3 Concept 9.1 DNA Structure Reflects Its Role as the Genetic Material In DNA, the number of purines is equal to the number of pyrimidines. a. True b. False c. I don t know.

4 Concept 9.1 DNA Structure Reflects Its Role as the Genetic Material On a piece of paper, draw the two backbones of the DNA helix. Be sure to label: the 5 and 3 ends the direction of the strand the phosphate and hydroxyl groups at each end What do the 5 and 3 refer to?

5 Concept 9.2 DNA Replicates Semiconservatively Suppose a cell s DNA has all been labeled (for example, with radioactive atoms or some other marker). The cell is then provided with unlabelled nucleotides, and is allowed to grow, replicate its DNA, and divide. Which of the following correctly describes the DNA that is in the daughter cells? a. Both strands are labeled. b. One stand is labeled and the other strand is not. c. Both strands are unlabeled. d. I don t know.

6 Concept 9.2 DNA Replicates Semiconservatively Discuss with a partner: Nucleotides are added to the 5 end of the growing DNA strand. a. True b. False c. I don t know.

7 Concept 9.2 DNA Replicates Semiconservatively With a partner, discuss why eukaryotes have multiple origins of replication while prokaryotes have only one.

8 Concept 9.2 DNA Replicates Semiconservatively The leading strand grows continuously at its end. a. backward; 5 b. forward; 5 c. backward; 3 d. forward; 3

9 Concept 9.2 DNA Replicates Semiconservatively Recall the two mechanisms for repairing errors in DNA replication. Working in pairs: Have one partner name and describe the mechanism that takes place during replication. Then have the other partner name and describe the mechanism that takes place after replication.

10 Concept 9.2 DNA Replicates Semiconservatively Draw a sketch illustrating why the lagging strand must be synthesized in small pieces, while the leading strand can be synthesized in one continuous piece. Label the 5 and 3 ends of all the strands of DNA in your sketch. When you are finished, compare your sketch with that of your neighbors.

11 Concept 9.2 DNA Replicates Semiconservatively Review with a partner the functions of the following enzymes. What does each of these enzymes do? DNA ligase Telomerase DNA polymerase Primase In what sequence do these enzymes usually work? Which of these enzymes would you expect to find in stem cells? Why?

12 Concept 9.3 Mutations Are Heritable Changes in DNA Suppose you re setting up a PCR reaction that should give you the last bit of data that you need to complete your Ph.D. thesis. You want this reaction to go well, because this is your last chance to use the lab s thermocycler before your dissertation defense. You add the PCR ingredients, place everything in the thermocycler (the machine that will do repeated rounds of heating and cooling), press start on the thermocycler, and go home. Once you re home you suddenly realize that you forgot to add one of the primers. 1. Name all the other ingredients that you did add correctly. 2. If you let the reaction run overnight, what will the products be? Will any DNA be made at all? If so, will it be the piece that you wanted? [Hint: You may wish to sketch out a molecule of DNA as it proceeds through several rounds of replication.] 3. Do you need to go back to the lab and start over?

13 Concept 9.3 Mutations Are Heritable Changes in DNA Working in pairs, describe to your partner in your own words what the following phrases mean. Take turns one person define one phrase, then the other person define the next, etc. Point mutation Deletion Inversion Translocation Duplication Silent mutation Gain-of-function mutation Loss-of-function mutation

14 Concept 9.3 Mutations Are Heritable Changes in DNA A mutation that occurs in body cells (i.e., skin cells) and is passed on to the daughter cells during mitosis, but is not passed on to sexually produced offspring, is called a(n) mutation. a. germline b. meiotic c. asexual d. somatic

15 Concept 9.3 Mutations Are Heritable Changes in DNA In sickle-cell disease, the sickle allele differs from the normal allele by how many base pairs? a. 0 b. 1 c. 2 d. 3 What type of mutation is this?