Introduction to Cell & Molecular Biology (BIOL121) - Dr. S.G. Saupe (ssaupe@csbsju.edu); Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321

Molecular Genetics - Study Guide

 

The mortal, living-and-dying individual is the transient care-taker of the instructions that must be conveyed down the generations...An individual life has significance only to the extent that it passes information about its ancestors to its descendents.

M. Hoagland

Required Reading:  text, Chapter 11, 12, 13, 14

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?)

  • conservative replication

  • semi-conservative replication

  • DNA polymerase

  • helicase

  • initiation site

  • leading strand

  • lagging strand

  • ligase

  • primase

  • replication bubble

  • Okazaki fragments

  • RNA primer

  • single strand binding protein

  • topoisomerase

Important Terms/Concepts - Transcription

  • activating enzyme

  • aminoacyl tRNA synthetase

  • general transcription factors

  • initiation site

  • non-template (non-coding, anti-sense) strand

  • promoter

  • ribozyme

  • RNA

  • RNA polymerase

  • rRNA, mRNA, tRNA

  • TATA box

  • template (coding, sense) strand

  • termination sequence

  • transcription factors

Important Terms/Concepts - Translation

  • codon

  • anticodon

  • �redundant� code

  • unambiguous code

  • intron

  • exon

  • spliceosome

  • leader sequence

  • AUG

  • initiation, elongation, termination

  • release factors

  • trailer sequence

  • pre-mRNA

  • mature mRNA

  • P site, A site

  • mutation - point, insertion, deletion, frameshift

  • reading frame

  • ribosome

  • wobble

Important Terms/Concepts - DNA Structure

  • 3',  5'

  • adenine

  • antiparallel

  • complementarity

  • cytosine

  • deoxyribose

  • DNA ligase

  • gene

  • guanine

  • helix

  • hydrogen bonds

  • nitrogenous base

  • nucleotide

  • purine

  • pyrimidine

  • ribose

  • thymine

  • uracil

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

  1. Explain how the structure of DNA molecule: (a) stores information, (b) allows for variability and diversity; (c) allows for mutability (mutation); and (d) allow for exact replication.

  2. Describe Hammerling�s experiments with Acetabularia and explain how these experiments, and those of Gurdon and Steward,  demonstrated 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

  6. Describe the structure of DNA

  7. Explain 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)

MatchingMatch each of the following with the appropriate scientist

a.  Avery et al.
b.  Chargaff
c.  Crick
d.  Franklin
e.  Griffith
f.  Gurdon
g.  Hammerling
h.  Hershey & Chase
i.   Miescher
j.  Meselsohn & Stahl
k.  Saupe
l.   Steward
m. Watson
n.  Wilkins
  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. _____ used 15N to study DNA replication
  13. _____ studied pus and sperm
  14. _____ studied sugar coated bacteria
  15. _____ suggested that adenine paired with thymine, guanine with cytosine
  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
  25. _____ demonstrated that DNA is replicated semi-conservatively

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.

3�  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

 5�

  T A C C C T T A A C C A A T G A G T A T T  


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?

3�  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

 5�

  T A C C C A T A A C C A A T G A G T A T T  

 

 

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?

3�  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

 5�

  T A C C C A T A A C C A A T C A G T A T T  

 

 

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.

3�  1 2 3 4     5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

 5�

  T A C C T G C T T A A C C A A T G A G T A T T  


 

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. 

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Last updated: July 14, 2009     � Copyright by SG Saupe