WORKSHEET #9 (Chapter 18) - Gene Expression - PDF

							WORKSHEET #9 (Chapter 18) - Gene Expression                                                 Due Date: ________________

Contributing group members:
_________________________ __________________________ _________________________ _________________________




        1) What is an operon?




        2) Make a table that compares the trp operon with the lac operon. In this table, include the following comaprisons:
           a. Are the genes in the operon part of a catabolic or anabolic pathway?
           b. The genes in the operon code for enzymes — what do the enzymes in each operon system do?
           c. Does each operon contain an operator? What does an operator do? Where is it located?
           d. What is the name of the regulatory gene for each operon?
           e. Without regulation, is this gene usually on or off?
           f. Without regulation, is the repressor usually in an active or inactive form?
           g. What effect does the presence of tryptophan (or lactose) have on the repressor and the overall expression of
           the gene?
           h. Why are both of these operons considered to be an example of negative gene control?



        3) Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of
           the following ways?
              A) allowing environmental changes to alter the prokaryote's genome
              B) allowing the organism to adjust to changes in environmental conditions
              C) allowing each gene to be expressed an equal number of times
              D) allowing young organisms to respond differently from more mature organisms
              E) organizing gene expression so that genes are expressed in a given order

Use the following scenario to answer the following questions.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic
genome.


        4) If she moves the operator to the far end of the operon, which of the following would likely occur when the cell is
           exposed to lactose?
              A) The operon will never be transcribed.
              B) The repressor protein will no longer be produced.
              C) The repressor will no longer bind to the operator.
              D) The inducer will no longer bind to the repressor.
              E) The structural genes will be transcribed continuously.




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 5) If she moves the repressor gene (lac I), along with its promoter, to a position at some several thousand base
    pairs away from its normal position, which will you expect to occur?
      A) The lac operon will be expressed continuously.
       B) The lac operon will function normally.
      C) The repressor will no longer be made.
      D) The repressor will no longer bind to the inducer.
       E) The repressor will no longer bind to the operator.


 6) Muscle cells and nerve cells in one species of animal owe their differences in structure to
      A) using different genetic codes.
       B) having different genes expressed.
      C) having unique ribosomes.
      D) having different chromosomes.
       E) having different genes.


 7) Two potential devices that eukaryotic cells use to regulate gene expression are _________________.
      A) cell differentiation and homeotic genes.                    B) DNA replication and methylation of histones.
      C) chromatin modification and protein processing.             D) histone amplification and DNA acetylation.


 8) The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an
    introduced double-stranded RNA is called
      A) RNA targeting.               B) RNA interference.           C) RNA obstruction.          D) RNA blocking.


 9) Which of the following best describes siRNA?
      A) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits
       B) a single-stranded RNA that can, where it has internal complementary base pairs, fold into cloverleaf
          patterns
      C) a molecule, known as Dicer, that can degrade other mRNA sequences
      D) a short double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
       E) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor


10) The process of cellular differentiation is a direct result of
      A) morphogenesis.                                              B) differences in cellular genomes.
      C) differential gene expression.                              D) cell division.


11) The general process that leads to the differentiation of cells is called
      A) determination.               B) specialization.             C) differentialization.      D) identification.




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12) Mutations in these genes lead to transformations in the identity of entire body parts:
      A) egg-polarity genes                                         B) segmentation genes
      C) morphogens                                                 D) homeotic genes


13) The fact that plants can be cloned from somatic cells demonstrates that
      A) differentiated cells contain masked mRNA.
      B) the differentiated state is normally very unstable.
      C) differentiation does not occur in plants.
      D) genes are lost during differentiation.
      E) differentiated cells retain all the genes of the zygote.


14) Which of the following serve as sources of developmental information?
      A) cytoplasmic determinants such as mRNAs and proteins produced before fertilization
      B) specific operons within the zygote genome
      C) paternally deposited proteins
      D) signal molecules produced by the maturing zygote
      E) ubiquitous enzymes such as DNA polymerase and DNA ligase




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