Unit 6 Review – Gene Expression
Essential knowledge 3.B.1: Gene regulation results in differential gene expression, leading to
cell specialization.
Regulation of Transcription:
1. DNA Regulatory Sequences- Regulatory sequences are stretches of DNA that
interact with regulatory proteins to control transcription.
Provide an example, from your notes, of each of these regulatory sequences.
• Promoters (Transcription Notes)
• Terminators (Transcription Notes)
• Enhancers (Video Tour Notes)
2. Regulatory Genes - A regulatory gene is a sequence of DNA encoding a regulatory
protein or RNA. Give two examples of how this gene works by using your lac operon
and tryp operon notes.
3. Small regulatory RNAs are involved in gene expression. Discuss exactly how RNAi
works by drawing a picture of the steps of the process. You may focus your
attention on siRNA instead of microRNA. (Video Tour Notes – Last animation)
3b. Give two tangible examples of RNAi in action using the animations on the top of
page 3 of your video tour.
a.
b.
Prokaryotic Positive and Negative Control Mechanisms in Gene Expression
For each of the following statements, explain using an example from your lac operon or tryp
operon notes.
1. Inducers - The expression of specific genes can be turned on by the presence of an inducer
(lactose).
2. Repressors - The expression of specific genes can be inhibited by the presence of a repressor
(tryptophan).
3. Inducers and repressors are small molecules that interact with regulatory
proteins and/or regulatory sequences (lactose and tryptophan).
4a. Regulatory Proteins- inhibit gene expression by binding to DNA and blocking
transcription (negative control).
4b. Regulatory proteins stimulate gene expression by binding to DNA and
stimulating transcription (positive control, CAP, and cAMP) or binding to repressors to
inactivate repressor function (repressor proteins).
6. Certain genes are continuously expressed; that is, they are always turned “on,”
e.g., the ribosomal genes. (O.K., I didn’t know that, but take a stab at why that needs to be the
case.)
Eukaryotic Gene Expression is Complex.
1. Transcription Factors - Transcription factors bind to specific DNA sequences and/or
other regulatory proteins.
a. Explain how transcription factors promote transcription using the first page of
your video tour notes.
b. Discuss how the p53 protein is a type of transcription factor. Use the second
page of your video tour.
2. Some of these transcription factors are Activators (increase expression), while
others are Repressors (decrease expression).
Draw two pictures…one of how an activator transcription factor works, and one of how
a repressor transcription factor works. (Video tour)
3. The combination of transcription factors binding to the regulatory regions at any
one time determines how much, if any, of the gene product will be produced.
Explain this statement.
4.
Gene regulation accounts for some of the phenotypic differences between
organisms with similar genes. Give an example of this from the Ghost in your Genes
video.