Lecture 17 - Control of Gene Expression

Question 1

Define structural genes, regulatory genes, and regulatory elements.

L17 S17

Answer 1

Structural genes:
-genes that encode for proteins

Regulatory genes:
-encode products that interact with other DNA/RNA sequences and affect transcription/translation

Regulatory elements:
-sequences that are not transcribed but regulate other sequences

Question 2

Define constitutive expression, positive control, and negative control.

L17 S18

Answer 2

Constitutive expression:
-continuous expression under normal conditions

Positive control:
-stimulation gene expression

Negative control:
-inhibition of gene expression

Question 3

What are different examples of how genes can be regulated at multiple levels?

L17 S19

Answer 3

Pre-transcriptional control
-alteration of DNA structure (compaction/relaxation)

Post-transcriptional control:

• mRNA processing
• alteration of RNA stability

Post-translational control:
-protein modification

Question 4

Differentiate between DNA binding domains and DNA binding motifs.

L17 S20

Answer 4

DNA binding domain:
-region of ~60-90 AAs that are responsible for DNA binding

DNA binding motif:
-portion of DNA binding domain that fits into the major groove of DNA

Question 5

What affect does histone acetylation have?

L17 S32

Answer 5

Histones tails have a positive charge that allows them to interact with the negative phosphates of DNA.

Acetylation lessens this positive charge and weakens the interaction of the two possibly allowing transcription factors for bind.

Question 6

What affect does chromatin remodeling have?

L17 S33

Answer 6

Histone can either be more or less closely packed thus preventing or allowing binding of transcription factors.

Question 7

What affect does DNA methylation have?

L17 S33

Answer 7

Methylation of cysteine bases adjacent to guanine bases (CpG rich sequences) typically suppress gene transcription.

Question 8

What are the functions of transcriptional activators and coactivators?

L17 S35

Answer 8

Activators:
-bind upstream sites and promote assembly of and stabilize transcription apparatus

Coactivators:
-protein complex that connects activator to polymerase

Question 9

What are transcriptional repressors, enhancers, and insulators?

L17 S39

Answer 9

Repressors:
-bind silencers and suppress transcription

Enhancers:
-assist in binding of nearby promoters

Insulators:
-blocks the effect of enhancers

Question 10

What is alternative splicing and what are its effects?

L17 S46

Answer 10

Usage of alternative splice sites during MRA processing. Can result in inclusion or exclusion of certain exons resulting in different proteins.

Question 11

What are some of the effects of miRNA?

L17 S51

Answer 11

• causes degradation of mRNA that it is complementary with
• causes inhibition of translation of mRNA that it imperfectly binds to
• attracts methylation enzymes for DNA that it is complementary to

Question 12

In RNA silencing, siRNAs and miRNAs usually bind to which part of the mRNA molecules that they control?

A. 5’ UTR
B. The segment that encodes amino acids
C. 3’ poly (A) tail
D. 3’ UTR

Answer 12

D. 3’ UTR