Concepts of Biology (BIOL115) - Dr. S.G. Saupe (ssaupe@csbsju.edu); Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321

Molecular Genetics - Study Questions

Required Reading:  Purves et al, Chapter 11 & 12.

Goal of the Unit:  The goal of this unit is to provide an introduction to the field of molecular genetics.  Our studies will focus on the structure of RNA and DNA, replication and how genes specify phenotype.

Important Terms/Concepts - Replication:  (can you use them in a conversation?  or make a concept map?  or crossword puzzle? or write an essay using them?)

Important Terms/Concepts - Transcription

Important Terms/Concepts - Translation

Important Terms/Concepts - DNA Structure

 Learning Objectives:  Upon completion of this unit you should be able to:

1. Explain how the structure of DNA stores information, allows for variability and diversity, mutability (mutation) and exact replication.

2. Describe Hammerling�s experiments with Acetabularia and explain how these experiments, and those of Gurdon and Steward,  demonstrate that the nucleus was the site of the genetic instructions in eukaryotic cells.

3. Explain why biologists earlier in the century believed that protein, but not DNA, is the molecule of inheritance.

4. Describe Griffith�s experiments.   What conclusions did he derive?

5. Describe the experiments/contributions of each of the following: Rosalind Franklin, Griffith; Chargaff; Avery et al.; Hershey & Chase; Beadle & Tatum; Watson & Crick; Gurdon

6. Describe the structure of DNA

7. Eexplain what a gene is, molecularly speaking, and explain why there is an infinite number of possible genes

8. Suggest reasons why Avery's conclusion that DNA, not protein, carried the genetic message, was not immediately accepted by biologists.

9. Answer the questions at the end of the chapter and on-line (course web site)

Matching:  Match each of the following with the appropriate scientist

1. _____ data provided evidence that DNA is a uniform thickness
2. _____ determined DNA is rich with phosphorus
3. _____ determined the structure of DNA
4. _____ female
5. _____ first to identify a transforming factor that could change bacterial strains
6. _____ nuclear transplant studies in algae showed that the nucleus contains the genetic instructions
7. _____ nuclear transplant studies in toads demonstrated that a single nucleus contains the genetic instructions to code for an entire organism
8. _____ really cool; looks like Brad Pitt; has been offered several Nobel Prizes but was too modest to accept them; sheep rancher
9. _____ showed that each plant cell has the genetic instructions to code for an entire new plant
10. _____ studied Acetabularia
11. _____ studied nitrogenous base content of various species
12. _____ studied pus and sperm
13. _____ studied sugar coated bacteria
14. _____ suggested that adenine paired with thymine, guanine with cytosine
15. _____ super dude; Bert Reynolds look-alike; wants to be a Big League baseball catcher when he grows up
16. _____ systematically digested components to determine the transforming factor was DNA
17. _____ used data from other scientists and built models
18. _____ worked with virulent and avirulent strains of pneumonia bacteria
19. _____ x-ray crystallographer
20. _____ data provided evidence that DNA is a helix
21. _____ data provided evidence that DNA replication is semi-conservative
22. _____ worked with bacteriophages
23. _____ tagged proteins with ³⁵S
24. _____ tagged DNA with ³²P

A Replication/Transcription/Translation Question
    The following represents the nucleotide sequence in the gene for a short polypeptide (protein).  The strand shown is the template (or "sense") strand.

1.  Replication:  Beneath the template (sense) strand above, write the nucleotide sequence for the non-template (anti-sense) strand of this segment of DNA.  Be sure to include the designation for the 3� and 5� ends.

2.  During replication of the sense strand, the anti-sense strand would be made from the:
        a.  right to the left      b.  left to the right

3.  If the DNA polymerase/replication fork moves along the DNA from the LEFT to the RIGHT replicating the DNA, the new complementary strand is made in:
        a.  one long piece       b.  a series of short fragments        c.  impossible to determine from the info provided

4.  In the space below, write the nucleotide sequence for the mRNA encoded by this gene.  Be sure to indicate the 3' and 5' ends for the mRNA.

5.  Circle the translation start codon in the mRNA in #4 above.

6.  What is the nucleotide sequence in the anti-codon loop of tRNA that is complementary to the start codon? ______.  Indicate the 3' and 5' side of the anti-codon region.

7.  What amino acid does the start codon specify?  ________

8.  Circle the translation stop codon in the mRNA strand in #4 above.

9. Using a codon table (see table in your text), in the space below write the predicted sequence of amino acids for the polypeptide encoded by this gene.

10.  Point Mutations - Assume that there is a point mutation in the DNA in nucleotide 6 and it is changed from T, which occurs in the original strand, to A as shown.   In the space below, write the amino acid sequence of the polypeptide that would result.  How will this mutation would this affect the final protein?

11.  More Point Mutations - Assume that there is a point mutation in the DNA in nucleotide 15 (red) and it is changed from G, which occurs in the original strand, to C as shown.   In the space below, write the amino acid sequence of the polypeptide that would result.  How will the mutation would this affect the final protein?

12.  Insertions.  Assume that two nucleotides, T and G are inserted in the original DNA strand between nucleotides 4 and 5.  How will this affect the polypeptide?  Write the sequence of amino acids in the protein below.

13.  Which one of the following would be likely to have the least impact on the final protein? (Explain)
    a.  an insertion involving one nucleotide   
    b.  an insertion involving two nucleotides
    c.  an insertion involving three nucleotides

14.  Assume that you isolate the polypeptide that was made in question #  above from a piece of �chicken-fried cat.�  To your surprise the protein begins with glycine!  What�s the deal?
    a.  the DNA, like a sleazy cat, lied
    b.  a methionine amino acid was probably clipped off the protein after translation
    c.  RNA polymerase made a mistake and inserted an incorrect nucleotide.