1. GENE REGULATION in Eukaryotic Cells
Biology, 9th ed,Sylvia Mader
Chapter 15
Gene Regulation
GENE REGULATION in Eukaryotic Cells
Every cell in a multi-cellular eukaryote has a copy of all genes.
However, different genes are actively expressed in
different cells
Chapter 15
Gene Regulation

2. Eukaryotic Regulation
Biology, 9th ed,Sylvia Mader
Eukaryotic Regulation
Chapter 15
Gene Regulation
A variety of mechanisms
Five primary levels of control:
Nuclear levels
Chromatin Packing
Transcriptional Control
Posttranscriptional Control
Cytoplasmic levels
Translational Control
Posttranslational Control
Chapter 15
Gene Regulation

3. Regulation of Gene Expression: Levels of Control in Eukaryotes
Biology, 9th ed,Sylvia Mader
Regulation of Gene Expression: Levels of Control in Eukaryotes
Chapter 15
Gene Regulation

4. Biology, 9th ed,Sylvia Mader
Chromatin Structure
Chapter 15
Gene Regulation
Eukaryotic DNA associated with histone proteins
Together make up chromatin
As seen in the interphase nucleus
Nucleosomes:
DNA wound around balls of eight molecules of histone proteins
Looks like “beads on a string”
Each bead a nucleosome
The levels of chromatin packing determined by degree of nucleosome coiling
Chapter 15
Gene Regulation

5. Levels of Chromatin Structure
Biology, 9th ed,Sylvia Mader
Levels of Chromatin Structure
Chapter 15
Gene Regulation

6. Biology, 9th ed,Sylvia Mader
Chapter 15
Chromatin Packing
Gene Regulation
Euchromatin
Loosely coiled DNA
Transcriptionally active
Heterochromatin
Tightly packed DNA
Transcriptionally inactive
Barr Bodies
Females have two X chromosomes, but only one is active
Other is tightly packed along its entire length
Inactive X chromosome is Barr body
Chapter 15
Gene Regulation

7. X-Inactivation in Mammalian Females
Biology, 9th ed,Sylvia Mader
X-Inactivation in Mammalian Females
Chapter 15
Gene Regulation

8. Biology, 9th ed,Sylvia Mader
Chapter 15
Gene Regulation
Non-Coding DNA
97% of human DNA is non-coding
Repetitive DNA not in genes
Tandemly repetitive DNA
short sequences repeated in series

9. Biology, 9th ed,Sylvia Mader
DNA Methylation
Chapter 15
Gene Regulation
The attachment of methyl groups to DNA bases
Inactivates the genes
Demethylating certain inactive genes turns them on.

10. Biology, 9th ed,Sylvia Mader
Histone Acetylation
Chapter 15
Gene Regulation
Acetyl groups attaching to histones
Acetylated histones grip DNA less tightly allowing for transcription to occur more easily

11. Transcriptional Control
Biology, 9th ed,Sylvia Mader
Transcriptional Control
Chapter 15
Gene Regulation
Transcription controlled by proteins called transcription factors
Bind to enhancer DNA
Regions of DNA where factors that regulate transcription can also bind
Always present in cell, but most likely have to be activated before they will bind to DNA
Chapter 15
Gene Regulation

12. Initiation of Transcription
Biology, 9th ed,Sylvia Mader
Initiation of Transcription
Chapter 15
Gene Regulation

13. Posttranscriptional Control
Biology, 9th ed,Sylvia Mader
Posttranscriptional Control
Chapter 15
Gene Regulation
Posttranscriptional control operates on primary mRNA transcript
Given a specific primary transcript:
Excision of introns can vary
Splicing of exons can vary
Determines the type of mature transcript that leaves the nucleus
May also control speed of mRNA transport from nucleus to cytoplasm
Will affect the number of transcripts arriving at rough ER
And therefore the amount of gene product realized per unit time
Chapter 15
Gene Regulation

14. Processing of mRNA Transcripts
Biology, 9th ed,Sylvia Mader
Processing of mRNA Transcripts
Chapter 15
Gene Regulation

15. Translational Control
Biology, 9th ed,Sylvia Mader
Translational Control
Chapter 15
Gene Regulation
Translational Control - Determines degree to which mRNA is translated into a protein product
Presence of 5′ cap
Length of poly-A tail on 3′ end
Posttranslational Control - Affects the activity of a protein product
Activation
Degradation rate
Chapter 15
Gene Regulation

16. Biology, 9th ed,Sylvia Mader
Chapter 15
Gene Regulation
Chapter 15
Gene Regulation