Gene Expression

Question 1

Operon

Answer 1

• found in prokaryotes
• cluster of genes that share a single promoter

Question 2

Transcriptional inhibitors (prokaryotes)

Answer 2

• repressors bind to the operator site, rendering RNA polymerase incapable of synthesizing mRNA

Question 3

Regulatory proteins in eukaryotes

Answer 3

• They have specific motifs (helix-turn-helix)

Question 4

Chromatin modification

Answer 4

Nucleosomes can modify positioning of chromosome to make promoter regions more or less accessible to regulatory proteins

Question 5

Posttranscriptional regulation: miRNA and siRNA

Answer 5

They bind to mRNA such that ribosomes cannot move any further during translation
- miRNA - repress genes different from their origin
- siRNA - repress genes from which they originated

Question 6

Posttranscriptional regulation: alternative splicing

Answer 6

Various proteins can be encoded by the same gene.
which alternative is expressed can be regulated

Question 7

Posttranscriptional regulation: RNA editing

Answer 7

RNA-binding proteins determine the stability of the RNA, hence affecting the duration of protein production

Question 8

Posttranscriptional regulation: Initiator complex modification

Answer 8

the initiation complex can be modified

Question 9

Protein degradation

Answer 9

• Protease in lysosomes
• Ubiquitin
  
  • proteins are tagged with ubiquitin
  • ubiquitinated proteins are degraded in proteasomes