Cell bio exam 2

Enhancer sequences are bound by:

•  

  RNA splicing complexes.

  
  

•  

  transcription factors.

  
  

•  

  cytosine methylation enzymes.

  
  

•  

  RNA editing complexes.

  
  

Promoters and enhancers are ___________________, and transcription factors are ____________________.

•  

  sequences of DNA important for regulation of transcription / proteins that bind to regulatory regions of genes

  
  

•  

  necessary for translation / necessary for transcription

  
  

•  

  necessary for transcription / necessary for translation

  
  

•  

  proteins that bind to regulatory regions of gene / sequences of DNA important for the regulation of transcription

  
  

Which of the following are polymers of amino acids?

•  

  transcription unit

  
  

•  

  RNA polymerase

  
  

• enhancer

•  

  transcription factor

  
  

• polypeptide

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?

•  

  RNA polymerase dissociates from the RNA.
  

  
  

•  

  The ribosome binds to the mRNA.

  
  

•  

  A guanine nucleotide with a methyl group is added to the 5. end of the mRNA.

  
  

•  

  The mRNA is polyadenylated at its 3' end.

  
  

Which of these processes are catalyzed by ribozymes? (Select all that apply.)

•  

  removal of introns in pre-mRNAs

  
  

•  

  peptide bond formation

  
  

•  

  transcription

  
  

•  

  DNA synthesis

  
  

•  

  phosphodiester bond formation

  
  

True or false: In a repressible operon, the presence of the repressor protein on the operator is required for the expression of the structural genes of the operon.

• True

• False

True or false: In the Lac operon, the binding of lactose to the repressor protein prevents the binding of the repressor protein to the operator.

• True

• False

Bacteria were grown in culture. At various time points, substances were added or removed from the culture medium. To assay the effects of the substances on operon gene expression, samples of bacteria were collected at one-minute intervals and levels of specific proteins and mRNAs were determined.

If arrow B indicates the addition of a substance, how could the operon be classified?

•  

  It is a repressible operon.

  
  

•  

  There is not enough information to classify the operon.

  
  

•  

  It is an inducible operon.

  
  

Bacteria were grown in culture. At various time points, substances were added or removed from the culture medium. To assay the effects of the substances on operon gene expression, samples of bacteria were collected at one-minute intervals and levels of specific proteins and mRNAs were determined.

If arrow B indicates the removal of a substance, how would the substance be classified?

•  

  an inducer

  
  

•  

  an operator

  
  

•  

  a co-repressor

  
  

•  

  a repressor

  
  

Protein structures have several different levels of organization. The primary structure of a protein is its amino acid sequence. The secondary and tertiary structures are more complicated. Consider the definitions below and select the one that best fits the term “protein domain.”

•  

  a complex of more than one polypeptide chain

  
  

•  

  a segment of a protein that folds independently

  
  

•  

  the tertiary structure of a substrate-binding pocket

  
  

•  

  a small cluster of α helices and β sheets