Welcome 1-29-16
 In your journal write a paragraph explain what is a gene
and what is gene expression?
 Notes on Gene Expression Regulation
 Quiz over DNA, RNA and Protein Synthesis
 HF: None  but you need to finish your project this
weekends, due next class!
Gene Regulation and Expression
Gene Regulation
Gene Regulation:
1. Modification of Genome (DNA)
• Chemical factors can structurally change the
DNA, turning it on or off.
– Chemical processes: DNA methylation & histone
modification
– Epigenome
• Gene regulation at the DNA level happens in
eukaryotes and rarely, if ever, in prokaryotes.
http://commonfund.nih.gov/epigenomics/f
Gene Regulation:
2. Transcriptional Regulation
• Transcriptional factors (regulatory
proteins) turn transcription on and off
or increase and decrease.
• This mechanisms happens in
eukaryotes and prokaryotes.
Prokaryotic Gene Regulation
DNA-binding proteins in prokaryotes regulate genes
by controlling transcription.
One of the keys to gene
transcription in bacteria is
the organization of genes
into operons.
Prokaryotes: Transcriptional
Regulation
• Operon – functioning unit of DNA containing the
following:
– A set of genes (DNA the codes for mRNA)
– Regulatory sections (DNA that controls the
expression of the gene)
Prokaryotes:
Transcriptional Regulation
Prokaryotes:
Transcriptional Regulation
The Lac Operon
When lactose is not
present, the lac genes are
turned off by regulatory
proteins that bind to DNA
and block transcription.
The Lac Repressor Blocks Transcription
When the lac repressor binds to the O region, RNA polymerase
cannot reach the lac genes to begin transcription.
Repressor
protein
Lactose Turns On the Operon
When lactose is added to the medium, it diffuses into the cell
and attaches to the lac repressor.
RNA
polymerase
Lactose
Repressor protein with
changed shape
Eukaryote:
Transcriptional Regulation
• Much more complicated and involves:
– Many regulatory proteins (transcription factors)
– Enhancers and TATA Box
Eukaryote:
Transcriptional Regulation
Gene Regulation
• One gene can result in several different proteins through a process
called:Alternate mRNA Splicing
Cell Specialization
Complex gene regulation in eukaryotes is what makes
differentiation and specialization possible.
Genetic Control of Development
Regulating gene expression
is important in shaping how a
multicellular organism develops.
Each of the specialized cell types
found in the adult originates from
the same fertilized egg cell.
Homeotic, Homeobox, and Hox Genes
 Homeotic genes
regulate organ
development.
 Homeobox genes
code for transcription
factors.
 Hox genes determine
the identities of each
body segment.
Environmental Influences
Environmental factors can
affect gene regulation.
Metamorphosis is an
example of how organisms
can regulate gene
expression in response to
change in their environment.
Check for understanding
1. Draw gene regulation flow map in your journal
2. What is gene expression and how gene
expression are regulated (be sure to include
modification of DNA, transcriptional regulation,
and post-transcriptional regulation)
3. Explain how does a gene turn on, and how
does it turn off. You can use lactose gene as an
example for your discussion.