Biology 165

Study Guide 4

Recommended text problems: : Chap. 16: 1-6, 8-14, Process of Science; Chap. 17:1-4, 5-16; Chap. 20: 1-2, 4, 6, 9, 14

Key Terms:

Adenine anticodon A site bacteriophage base codon Cytosine DNA DNA ligase DNA polymerase I DNA polymerase III

Double helix Exon Frameshift mutation Genetic code Gene Genotype Guanine helicase intron missense mutation mRNA

mutation nonsense mutation Nucleotide Okazaki fragment P site PCR Phosphodiester bond Promoter Protein Recombinant DNA

Reverse transcriptase Ribose Ribosome RNA polymerase rRNA Semi-conservative replication Thymine Transcription Translation tRNA uracil

Questions:

1. Before the 1940’s proteins were though to be the basis of the genetic material. Why did scientists think this? Review the experiments that convinced us that the genetic material is actual DNA, not proteins. Know the names of the experimenters, and what their work showed.

2. There are several key experiments involved in the study of DNA. Know the experiments performed by the following researchers: 1) Griffiths; 2) Avery, MacLeod, McCarty; 3) Hershey& Chase; 4) Messelson & Stahl. Know the methods they used, the hypothesis they were testing, what their results showed.

3. DNA replication is called “semi-conservative”. What does this mean? What are the end products of DNA replication?

4. DNA replication is also called “semi-discontinuous”. What does this mean? What property of DNA polymerase accounts for this means of DNA replication?

5. What are the functions of the following? Helicase, DNA pol I, DNA pol III, DNA ligase, primase, single-stranded binding proteins, topoisomerase, RNA polymerase.

6. Be careful not to confuse the processes of DNA replication, transcription, and translation. Know the functions of each, the product of each, the enzymes involved in each, and the steps of each. Construct a table with 3 columns labeled replication, transcription, and translation. Under each heading, list all of the components listed above.

7. Trace the production of a protein in a eukaryotic cell, starting with the DNA in the nucleus through transcription and translation. What enzymes are involved? Where does each step take place?

8. After a gene is transcribed in eukaryotes, what steps must be performed on the RNA transcript before it can be translated? Draw an RNA molecule that has just been transcribed and then one that has undergone the processing that you just described. What differences are there?

9. How does RNA polymerase “know” where to start transcription of a gene? How does a ribosome “know” where to start translating an mRNA strand?

10. What happens in the following steps of translation: initiation, elongation, termination? What roles do the “start codon” and the “stop codons” play? The A site and the P site?

11. Compare and contrast each of the following: mRNA, tRNA, rRNA. What are the functions of each?

12. mRNA strand has the sequence 5’-AUG UUC CGA GGC AAG UGA-3’. What is the sequence of 1) the template DNA 2) the coding strand of DNA 3) the polypeptide produced. Be sure to include 5’ and 3’ ends!

13. Draw the structure of a tRNA molecule with an anticodon that reads UAC. What would be the mRNA codon this tRNA would bind to? What amino acid would be attached to this tRNA?

14. What does PCR do? What are the steps in PCR? What reactants do you need to perform PCR?

15. Compare and contrast missense, nonsense, silent, and frameshift mutations. Which do you think would have the most severe effect on the phenotype?